This has been CNBC's live blog covering updates on the war in Ukraine. Follow the latest updates here.

U.S. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin visited Ukraine on Sunday to discuss military aid with Ukraine's President Volodymyr Zelenskyy.

At the meeting in Kyiv — which was shrouded in secrecy and the highest-level visit to Ukraine by U.S. officials since the invasion began — the U.S. pledged just over $700 million in military financing to help Ukraine and other allied countries in central and eastern Europe involved in the war effort.

The U.S. State Department approved a potential sale of $165 million in ammunition to Ukraine. Meanwhile, President Joe Biden spoke to newly reelected French President Emmanuel Macron, and the two leaders pledged close cooperation on global affairs as Russia maintains its assault on its neighbor.

Russia's invasion of Ukraine entered its third month on Sunday. The conflict has killed thousands and led to the worst refugee crisis Europe has seen since World War II.

The war will end only if Russian troops fully withdraw from the country, Ukrainian Prime Minister Denys Shmyhal said.

International Criminal Court to join multinational investigation into alleged international crimes in Ukraine

The International Criminal Court's prosecution office will join a joint investigation team set up by Lithuania, Poland and Ukraine to investigate alleged international crimes committed during the Ukraine war.

ICC Prosecutor Karim Khan signed an agreement with the prosecutors general of the three countries Monday.

"With this agreement, the JIT parties and the Office of the Prosecutor are sending a clear message that all efforts will be undertaken to effectively gather evidence on core international crimes committed in Ukraine and bring those responsible to justice," the European Union's judicial cooperation agency said in a statement.

— Chelsea Ong

UK says Ukraine's grain harvest is likely to be about 20% lower than in 2021

Russia's invasion has "significantly" disrupted Ukrainian agricultural production, the British defense ministry said in an intelligence update.

"The Ukrainian grain harvest for 2022 is likely to be around 20 per cent lower than 2021 due to reduced sowing areas following the invasion," the U.K. ministry said.

Reduced grain supply from Ukraine — the world's fourth largest producer and exporter of agricultural goods — would not only cause inflationary pressures and elevate the global price of grain, but also impact global food markets, the ministry said.

Grain prices have surged since the invasion began, and Morgan Stanley expects grain prices to remain above last year's levels till 2023.

"High grain prices could have significant implications for global food markets and threaten global food security, particularly in some of the least economically developed countries," the British ministry said.

— Chelsea Ong

Schumer expects 'swift, bipartisan' passage of next Ukraine aid bill

U.S. Senate Majority Leader Chuck Schumer said he expected "swift, bipartisan" passage of another bill to aid Ukraine in its fight against Russia once President Joe Biden submits a new funding request.

— Reuters

Mariupol officials say new mass grave found

Officials in the embattled Ukrainian city of Mariupol say a new mass grave has been identified north of the city.

Mayor Vadym Boychenko said authorities are trying to estimate the number of victims in the grave about 10 kilometers (about 6 miles) north of Mariupol.

Satellite photos released over the past several days have shown what appear to be images of other mass graves.

Mariupol has been decimated by fierce fighting over the past two months. The capture of the city would deprive Ukraine of a vital port and allow Moscow to establish a land corridor to the Crimean Peninsula, which it seized from Ukraine in 2014.

— Associated Press

Spring has sprung in Kyiv

Residents of the Ukrainian capital Kyiv can walk freely in the streets and at the city's parks, and enjoy a beautiful spring day after weeks of Russian attacks.

— Anadolu Agency | Getty Images

Biden and newly reelected Macron speak, agree to deepen ties amid Russia's war in Ukraine

President Joe Biden spoke with newly reelected French President Emmanuel Macron, according to a White House readout of the call.

The U.S. president called to congratulate Macron a day after France's election, a French presidential source confirmed to NBC News. On Sunday, France elected Macron for a second term as president over Marine Le Pen, the nationalist and far-right National Rally candidate.

Biden said he was ready to continue working closely with Macron on their shared global priorities, according to a White House readout of the call. The Élysée Palace source said the two leaders would have a follow-up call to talk about additional ways to support Ukraine amid Russia's invasion.

In a two-hour TV debate last week, Macron called out Le Pen's previous ties with Russian President Vladimir Putin and accused her of being dependent on Moscow. Le Pen's links to Putin drew particular scrutiny because of the Kremlin's war in Ukraine and the major role France has played in supporting Kyiv.

 — Amanda Macias

State Department approves potential sale of $165 million in ammunition to Ukraine

The State Department announced a possible sale of approximately $165 million of non-standard ammunition to Ukraine.

Non-standard ammunition includes rounds for Soviet-made military equipment that Ukraine has in its arsenal.

Secretary of State Antony Blinken determined that the foreign military sale is justified given the Kremlin's ongoing war in Ukraine.

 — Amanda Macias

UN chief Guterres, Turkey's Erdogan stress need to end humanitarian crisis in Ukraine

The U.N. says Secretary-General Antonio Guterres and Turkey's President Recep Tayyip Erdogan are stressing the urgent need for "effective access through humanitarian corridors" to evacuate Ukrainian civilians and deliver humanitarian aid to communities impacted by the war.

Guterres met Erdogan in Ankara and expressed support for Turkey's ongoing diplomatic efforts to end the war, U.N. spokesman Stephane Dujarric said, adding that they "agreed to stay in contact to follow up on ongoing initiatives."

The U.N. chief and the Turkish president "reaffirmed that their common objective is to end to the war as soon as possible and to create conditions to end the suffering of civilians," Dujarric said.

During the meeting, Erdogan also said Turkey would continue to work closely with the U.N. to end the humanitarian crisis in Ukraine and to help in the evacuation of civilians.

Guterres is scheduled to travel to Moscow to meet Russian President Vladimir Putin on Tuesday and will then head to Kyiv to meet Ukrainian President Volodymyr Zelenskyy on Thursday. The Ukrainian leader has criticized the secretary-general for visiting Moscow before going to Kyiv.

— Associated Press

Russia investigates cause of large oil depot fire near Ukraine

Russia said it would investigate the cause of a large fire that erupted in the early hours of the morning at an oil storage facility in the city of Bryansk 154 km (96 miles) northeast of the border with Ukraine.

— Reuters

Traders say Rosneft oil tender fails after it demands ruble payment

Russia's Rosneft failed to sell oil in a jumbo tender after demanding prepayment in rubles, five traders said on Monday, meaning the country's top oil company will need to find ways to divert more crude to buyers in Asia via private deals.

The failure of the tender highlights a growing struggle by the Kremlin oil major to sell oil due to sweeping Western sanctions on Russia for the invasion of Ukraine.

Moscow, which calls the invasion "a special operation," has publicly acknowledged it has faced some oil export problems since March due to sanctions but pledged to boost cooperation with Asia to divert some oil sales from the West.

Western sanctions on Russian oil are part of a broader effort to isolate Moscow politically and economically for the invasion that includes discussion of an EU-wide oil embargo. The European Union also advised its members not to succumb to Russian President Vladimir Putin's demand to pay rubles for gas from Russian gas monopoly Gazprom.

— Reuters

No agreement on Mariupol humanitarian corridor for thousands stuck in steel plant: Ukraine deputy PM

Ukraine has not agreed on a humanitarian corridor with Russia to evacuate the civilians stuck in the Azovstal steel complex in the besieged city of Mariupol, its Deputy Prime Minister Iryna Vereshschuk said.

Earlier in the day, Russia's defense ministry said it was opening a humanitarian corridor for the civilians — who number up to 1,000 according to the Ukrainian government — to leave the steel plant.

This "could be believed if the Russians had not broken the humanitarian corridors many times before," Vereshschuk said in a post on Telegram, translated by Google. "I know what I am saying because, on behalf of the President, I am personally conducting such negotiations and organizing humanitarian corridors."

Multiple previous attempts to establish these corridors have failed, with Kyiv blaming Russian forces for not holding their fire to allow safe passage. Moscow meanwhile blames Ukrainian forces for the failure.

"It is important to understand that the humanitarian corridor is opened by agreement of both parties," Vereshschuk added. "The corridor, announced unilaterally, does not provide security, and therefore, in fact, is not a humanitarian corridor. So, I declare officially and publicly: unfortunately, there are no agreements on humanitarian corridors from Azovstal today."

Vereshschuk said her government asked UN Secretary-General Antonio Gutteres to initiate and guarantee the Azovstal humanitarian corridor for civilians, calling for UN and International Committee of the Red Cross representatives be present there.

"We hope for the effectiveness of the UN Secretary General's talks with the Russian representatives," she added.

— Natasha Turak

UN says 2,665 killed in Ukraine since start of war, warns death toll is likely higher

The United Nations says it has confirmed 2,665 civilian deaths and 3,053 injuries in Ukraine since Russia invaded its ex-Soviet neighbor on Feb. 24.

Of those killed, the U.N. has identified at least 59 girls and 69 boys, as well as 67 children whose gender is unknown.

The Office of the UN High Commissioner for Human Rights said Monday that the death toll in Ukraine is likely higher, citing delayed reporting due to the armed conflict.

The international body said most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple launch rocket systems, as well as missiles and airstrikes.

 — Amanda Macias

Ukraine's foreign minister blasts 'excuses and half-measures' from EU on Russian energy use

Ukrainian Foreign Minister Dmytro Kuleba criticized European Union leaders, saying they must do more to end their purchases of Russian oil and gas.

"If world leaders and businesses are serious about ending Russian war crimes, they must first deprive Putin of oil revenues," Kuleba wrote on Twitter.

"EU needs a real embargo on Russian oil," a second tweet from Kuleba said. "Additionally, Russia desperately tries to bypass the already imposed restrictions. Let's be clear: any blend containing any Russian oil should be treated as 100% Russian oil. Don't let Russians cheat their way around restrictions."

The EU imported roughly 37% of its oil and 24% of its total energy (excluding renewables and nuclear) from Russia in 2020, according to Eurostat. Some EU leaders have shown a willingness to sanction Russian energy, but many of the bloc's countries strongly oppose such a move as their economies are heavily dependent on those imports and fuel prices are already at historic highs.

— Natasha Turak

Biden to nominate career diplomat Bridget Brink as U.S. Ambassador to Ukraine

President Joe Biden is set to nominate Bridget Brink to serve as the U.S. ambassador to Ukraine.

Brink, a career diplomat, currently serves as the U.S. ambassador to the Slovak Republic. During her 25-year career in the Foreign Service, she has focused on advancing U.S. policy in Europe and Eurasia, the White House said in a statement. Originally from Michigan, Brink speaks Russian and has studied Slovak, Serbian, Georgian and French.

Secretary of State Antony Blinken alongside Secretary of Defense Lloyd Austin told Ukrainian President Volodymyr Zelenskyy on Sunday that the U.S. will start to return diplomats to Ukraine as early as this week.

Blinken said that U.S. diplomats will start with day trips into the western city of Lviv and other parts of the country and ultimately, to resume their presence in Kyiv.

 — Amanda Macias

Russian ambassador to Washington warns against sending more weapons to Ukraine

Russian ambassador to Washington Anatoly Antonov criticized U.S. weapons support for Ukraine, speaking on Russian state television.

"We stressed the unacceptability of this situation when the United States of America pours weapons into Ukraine, and we demanded an end to this practice," Antonov told TV channel Rossiya 24, according to a Reuters translation.

The ambassador said that an official diplomatic message had been delivered to Washington expressing Russia's opposition on the heels of U.S. Secretary of State Antony Blinken's visit to Kyiv.

During that visit, Blinken pledged hundreds of millions more dollars in weapons aid to Ukraine and Secretary of Defense Lloyd Austin said the U.S. wanted to see Russia "weakened" to the point that "it cannot do the kinds of things it has done in invading Ukraine."

— Natasha Turak

Russian rockets hit central region of Vinnytsia, governor says

Russian rockets hit infrastructure in two towns in Ukraine's central Vinnytsia, regional governor Serhiy Borzov said.

"Today, Vinnytsia region is once again under rocket fire (in) the towns of Zhmerynka and Kozyatyn. The enemy is attempting to hit critical infrastructure," Borzov said in a video message delivered on the Telegram app, according to a Reuters translation.

The number of casualties has not been specified, and NBC has not independently verified the reports.

— Natasha Turak

Russia has 'already failed,' Blinken says during Kyiv visit

Russia has already failed in its key goal of its invasion of Ukraine, U.S. Secretary of State Antony Blinken said during his visit to Kyiv.

"In terms of Russia's war aims, Russia has already failed, and Ukraine has already succeeded, because the principal aim that President Putin brought to this, in his own words, was to fully subsume Ukraine back into Russia, to take away its sovereignty and independence," Blinken said, addressing a pool of press. "And that has not happened, and clearly will not happen."

Russian President Vladimir Putin's aim was to topple Ukraine's government and completely "demilitarize" Ukraine, and Moscow reportedly expected that Kyiv would fall to its control within days.

Instead, Russia has lost at least seven generals, 3,000 pieces of large equipment and as many as 20,000 troops during its nine-week war against its much smaller neighbor, according to NATO estimates, Ukrainian government reports and open-source intel tracker Oryx. It has still not managed to gain air superiority over the country, thanks to stiff Ukrainian resistance and a high volume of weapons and intelligence support from NATO countries.

— Natasha Turak

'We want to see Russia weakened,' U.S. Defense Secretary Austin says

Washington wants to see Russia "weakened" as part of its aims in arming and supporting Ukraine, Defense Secretary Lloyd Austin said Monday during a visit to Kyiv, the first such high-level visit from a U.S. official since the war began.

"We want to see Ukraine remain a sovereign country, a democratic country able to defend its sovereign territory. We want to see Russia weakened to the degree that it cannot do the kinds of things it has done in invading Ukraine," Austin told the press.

"It has already lost a lot of military capability, and a lot of its troops, quite frankly. In terms of our — their ability to win, the first step in winning is believing that you can win. And so, they believe that they can win, we believe that they can win, if they have the right equipment."

The visit saw the U.S. pledge more military and diplomatic support to Ukraine as the Russian invasion entered its 60th day.

— Natasha Turak

Global military spending topped $2 trillion in 2021, new data shows

Total global military expenditure reached an all-time high of $2.1 trillion in 2021, according to new data on global military spending published today by the Stockholm International Peace Research Institute.

The five largest spenders last year were the United States, China, India, the U.K. and Russia, together accounting for 62% of expenditure, SIPRI said. This was the seventh consecutive year that spending increased.

Russia increased its military expenditure by 2.9% in 2021 to $65.9 billion, at a time when it was building up its forces along the Ukrainian border, the institute noted.

This was the third consecutive year of growth for Russia's military spending, which reached 4.1% of gross domestic product in 2021.

As it has strengthened its defenses against Russia, Ukraine's military spending has risen by 72% since the annexation of Crimea in 2014. Spending fell in 2021 to $5.9 billion, but still accounted for 3.2% of the country's GDP.

— Holly Ellyatt

UK says Russia has not made a 'significant breakthrough'

Russia has yet to achieve a "significant breakthrough" since shifting its focus on the Donbas region of eastern Ukraine, the British defense ministry said in an intelligence update.

The ministry said Russian forces lack "sufficient logistical and combat support enablers" and has only made "minor advances" in the region.

Ukraine's defense of Mariupol has exhausted many Russian units and reduced their combat effectiveness, the British defense ministry said.

"Russia's decision to besiege rather than attack Mariupol's Azovstal steel plant means many Russian units remain fixed in the city and cannot be redeployed," the it added.

Several thousand Ukrainian troops and civilians remain holed up in the Azovstal steel plant in the besieged city of Mariupol. The site has become one of the last significant holdouts of Ukrainian forces in an otherwise Russian-occupied city.

Russia's defense ministry has also proposed that compensation payments for the families of deceased Russian troops be overseen by military rather than civilian officials, the British ministry said.

"This likely reflects a desire to hide the true scale of Russia's losses from the domestic population," the ministry added.

— Chelsea Ong

U.S. pledges more military aid for Ukraine and plans to eventually re-open embassy in Kyiv

U.S. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin arrived in Ukraine to discuss military aid with Ukraine's President Volodymyr Zelenskyy on Sunday.

The visit, which saw the senior U.S. officials meet with Ukraine's Foreign Minister Kuleba as well as the country's defense and interior ministers, saw both sides discuss the U.S.' continued "security assistance, economic assistance and humanitarian assistance" for Ukraine, one senior official said in a background briefing on the visit.

Three significant announcements were made following the visit:

Firstly, that President Biden will formally nominate Bridget Brink, currently the U.S.' ambassador to Slovakia to be the next U.S. ambassador to Ukraine.

Secondly, U.S. diplomats will be returning to Ukraine as early as this week, starting with day trips into the western city of Lviv then graduating to potentially other parts of the country and ultimately, to resume their presence in Kyiv. A senior state department official said Sunday that "we'll seek to have our diplomats return to our embassy in Kyiv as soon as possible."

Lastly, that the U.S. has pledged more than $713 million in foreign military financing, including funding for Ukraine and 15 other allied and partner nations in Central and Eastern Europe and the Balkans.

The aid will include support for Ukraine to transition from outdated Soviet-era weapons to more modern ones used by NATO members.

Blinken also informed President Zelenskyy some of the howitzer artillery systems the U.S. previously announced it would provide have arrived. Seven more howitzer packages will also be sent to Ukraine imminently, a senior defence official said.

 — Holly Ellyatt and Chelsea Ong

UK says Russia is planning a staged poll in a Ukrainian city to legitimize its occupation

Russia is planning a staged referendum in Kherson, Ukraine, to justify its occupation, the British defense ministry said in an intelligence update.

The southern city is important to Moscow's objective of establishing a land bridge to Crimea and dominating southern Ukraine, the U.K. Defense Ministry said in a tweet.

The Crimea peninsula, which Russia illegally seized control of in 2014, lies to the south of Ukraine between the Black Sea and the Sea of Azov. It is separated from Russia to the east by the narrow Kerch Strait.

The ministry noted that Russia previously held a "illegitimate referendum" in Crimea in 2014 to retrospectively legitimize the accession of the peninsula into the country.

"Russia's own domestic elections have been beset by allegations of vote rigging and have seen high-profile opposition blocked from running," the ministry added.

— Chelsea Ong

Zelenskyy meets top-level U.S. delegation, Ukraine official says

The U.S. secretaries of state and defense met Sunday night with Ukrainian President Volodymyr Zelenskyy in the highest-level visit to the war-torn country's capital by an American delegation since the start of Russia's invasion.

The meeting with U.S. Secretary of State Antony Blinken and U.S. Defense Secretary Lloyd Austin was confirmed by presidential adviser Oleksiy Arestovych in an interview on Ukrainian TV.

It came as Ukraine pressed the West for more powerful weapons against Russia's campaign in the Donbas region of eastern Ukraine, where Moscow's forces sought to dislodge the last Ukrainian troops in the battered port of Mariupol.

"Yes, they're meeting with the president. Let's hope something will be decided on further help," Arestovych said in an interview on Ukrainian TV.

Before the session, Zelenskyy said he was looking for the Americans to produce results, both in arms and security guarantees.

"You can't come to us empty-handed today, and we are expecting not just presents or some kind of cakes, we are expecting specific things and specific weapons,'' he said.

—Associated Press

Ukraine blames Russia after Mariupol humanitarian corridor fails

No humanitarian routes were established out of the besieged southeastern Ukrainian port city of Mariupol, Ukraine's Deputy Prime Minister Iryna Vereshchuk said, blaming Russian forces for not holding their fire.

Vereshchuk said the Ukrainian side would try again on Monday to establish safe passage out of Mariupol. She called for U.N. Secretary General Antonio Guterres, who is scheduled to travel to Moscow before visiting Kyiv this week, to demand a ceasefire and open up humanitarian corridors from Mariupol.

"This is what Guterres should talk about in Moscow, if he is preparing to talk about peace," Vereshchuk said.

—Reuters

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Zelenskyy presses senior U.S. officials for more powerful weapons; Mariupol humanitarian corridor fails