This has been CNBC's live blog covering Tuesday's updates on the war in Ukraine. [Follow the latest updates here.]
Russia claimed it would reduce its attacks on Ukraine as delegates from the two countries met for their latest face-to-face peace talks in Istanbul.
Moscow said it would cut back its military activity near Ukraine's capital of Kyiv and the northern city of Chernihiv, though Russia has not followed through on similar pledges in the past.
Ukrainian officials have pushed for a cease-fire agreement and a resolution to the humanitarian crisis sparked by Moscow's invasion. After the day's talks ended, an official from Ukraine's delegation called for an international security guarantee similar to NATO's Article 5.
Russia is trying to buy more time through negotiations with Ukraine, according to Melinda Haring of the Atlantic Council.
"It is an attempt for the Russians to buy more time so that they can come back in, regroup and come back stronger," said Haring, who is deputy director of the Atlantic Council's Eurasia Center.
Moscow said overnight that it will scale back its military activity near the Ukrainian capital of Kyiv and the northern city of Chernihiv, but the Pentagon has cautioned it's not a retreat. Russia previously did not followed through with similar pledges.
"Nothing has changed today, that's the important point," Haring added.
"The bottom line is that Ukraine has to continue to fight, and fight very valiantly, and inflict major costs on Russia until Russia is ready to actually engage in real negotiations," The West will also need to continue to send defensive material to Ukraine, she added.
It will take "many more weeks and many more months" until the Russians will be willing to really negotiate, she said.
— Chelsea Ong
Russia's announcement that it is pulling its troops back from Kyiv is a "distraction" from their plan to move the "real fighting" to eastern Ukraine, says Christopher Miller, assistant professor of international history at The Fletcher School at Tufts University.
"[The announcement] is just a statement of the military reality that Ukrainians had pushed them back somewhat," Miller told CNBC's "Squawk Box Asia" on Wednesday.
U.K. and U.S. officials have recently made similar determinations. Military movements in Ukraine are difficult or impossible to confirm as the situation on the ground changes constantly.
The Donbas in eastern Ukraine will be crucial for Russia to "eke out something" that looks like a victory to sell to their populous, which is why Moscow is "doubling down" on this region, said Miller who is also co-director of the school's Russia and Eurasia program.
"It's trying to grab enough territory to package it as a success at home and justify the cost of this war, which was far higher than anyone in Russian government and certainly the Russian populace was setting up," he added.
"I don't think we're anywhere close to the end of the war at this point," Miller said.
— Chelsea Ong
The Russian military has begun to move some of its troops in Ukraine away from the areas around Kyiv to positions elsewhere in Ukraine, Pentagon Press Secretary John Kirby said Tuesday.
The movements mark what the Pentagon says is a strategic shift in the invasion that began early on Feb. 24.
"Up until recently, we had still assessed that their plan was was to occupy and annex Ukraine using approaches along three lines of attack," Kirby told reporters at the Pentagon. "Now we think they're going to prioritize the east" of Ukraine.
Still, Kirby cautioned that the troop movements do not amount to a retreat, as some observers had speculated. "We believe that this is a repositioning, not a real withdrawal," he said.
— Christina Wilkie
The State Department welcomed a slew of recent expulsions of Russian intelligence officers serving under the cover of diplomatic missions in European countries.
In a coordinated move, Ireland, Belgium, the Netherlands and the Czech Republic expelled a total of 43 Russian diplomats suspected of spying. Poland also took similar steps in the past week.
"As our partners have outlined, these actions are in response to these individuals' activities, which are in contravention of their diplomatic status and the Russian Federation's aggression in Ukraine," wrote State Department spokesman Ned Price in a statement.
"We stand unified with our partners in protecting their national security from the Russian Federation's intelligence threats and against threats to democracy," Price added.
– Amanda Macias
Deputy U.S. Secretary of State Wendy Sherman warned that Russia's war in Ukraine has exacerbated a global food crisis already worsened by Covid-19.
"The responsibility for waging war on Ukraine and for the war's effects on global food security falls solely on President Putin," Sherman said in a speech at the United Nations.
Sherman said that Russian warships are blocking access to Ukraine's ports, essentially cutting off exports of grain. "They're reportedly preventing approximately 94 ships carrying food for the world market from reaching the Mediterranean," Sherman said, adding that food prices around the world are skyrocketing.
Sherman said that nearly half of Ukrainians are unable to access food. She added that people feel the war's effects on food security "far beyond Ukraine's borders."
"We are particularly concerned about countries like Lebanon, Pakistan, Libya, Tunisia, Yemen and Morocco which rely heavily on Ukrainian imports to feed their populations," she said.
– Amanda Macias
President Joe Biden does not regret saying that Russian leader Vladimir Putin "cannot remain in power," the White House said in response to further questioning about the eyebrow-raising ad-lib in a speech on Saturday.
"Absolutely not, he spoke from the heart as he always does," White House communications director Kate Bedingfield said when asked at a press briefing if Biden regretted making the remark, which overshadowed the rest of the sweeping speech he delivered in Warsaw, Poland.
"He speaks from the heart, he says what he feels, and no, he absolutely does not regret that in any way," Bedingfield said.
Biden himself stood by the comment, telling reporters Monday that he was expressing "moral outrage" but not announcing a policy "to take Putin down."
— Kevin Breuninger
America's top commander in Europe told lawmakers that the U.S. has observed multiple Russian launches of hypersonic weapons into Ukraine.
"I think it was to demonstrate the capability and attempt to put fear in the hearts of the enemy and I don't think they were successful," U.S. Air Force General and NATO Supreme Allied Commander Tod Wolters said during testimony before the Senate Armed Services Committee.
Wolters, who also serves as commander of U.S. European Command, did not specify the number of hypersonic missiles launched. The missiles travel five times faster than the speed of sound.
Last week, a senior U.S. Defense official who spoke on the condition of anonymity questioned why the Kremlin would need to fire a hypersonic missile "from not that far away" to hit a building in Ukraine.
Since Russia invaded its ex-Soviet neighbor last month, the Pentagon has observed more than 1,370 Russian missile launches into Ukraine.
Wolters also told lawmakers that the U.S. believes Russian President Vladimir Putin has dedicated about 75% of his entire military force to the fight in Ukraine.
– Amanda Macias
Firemen work to control a blaze at a large fuel base located near Ukraine's western settlement of Klevan in the Rivne region. The facility supplies fuel to Kyiv for the Ukrainian army.
Russia hit the structure with high-precision air-launched cruise missiles.
— Getty Images / Reuters
U.S. President Joe Biden and four key European leaders discussed efforts to hamper Russia's economy and provide military and humanitarian aid to Ukraine during a hastily arranged call.
Biden spoke with U.K. Prime Minister Boris Johnson, German Chancellor Olaf Scholz, French President Emmanuel Macron and Italian Prime Minister Mario Draghi as Ukrainian and Russian officials held peace talks in Istanbul. The four officials lead the largest economies in Europe.
"The leaders affirmed their determination to continue raising costs on Russia for its brutal attacks in Ukraine, as well as to continue supplying Ukraine with security assistance to defend itself against this unjustified and unprovoked assault," the White House said in a readout of the call.
"They reviewed their efforts to provide humanitarian assistance to the millions affected by the violence, both inside Ukraine and seeking refuge in other countries, and underscored the need for humanitarian access to civilians in Mariupol," it continued. "They also discussed the importance of supporting stable energy markets in light of current disruptions due to sanctions."
Neither the Biden administration readout nor a similar summary from the U.K. government mentioned Russia's claim that it would scale back military operations near Ukraine's capital of Kyiv.
— Jacob Pramuk
Russian forces have killed at least 1,179 civilians since Moscow invaded Ukraine, according to the United Nations.
At least an additional 1,860 people were injured, including 74 children, from Feb. 24 through March 28, the Office of the UN High Commissioner for Human Rights said.
The majority of deaths recorded were caused by explosive weapons with a "wide impact area," the office said. That includes shelling from heavy artillery and airstrikes.
The agency said it believes the actual number of casualties are "considerably higher," since information from areas with intense fighting is delayed and some reports are being corroborated.
– Amanda Macias
A $50 million Russian-owned superyacht docked in London's Canary Wharf financial district was detained by British authorities.
Motoryacht Phi, designed by shipbuilders Royal Huisman, includes an "infinite wine cellar" and a patented fresh-water swimming pool, according to Britain's National Crime Agency.
"The ownership of the yacht was deliberately well hidden. The company the ship is registered to is based in the islands of Saint Kitts and Nevis and it carried Maltese flags to hide its origins," the U.K. National Crime Agency wrote in a statement.
U.K. Transportation Secretary Grant Shapps said that the detention of the yacht "turned an icon of Russia's power and wealth into a clear and stark warning to Putin and his cronies."
"Detaining the Phi, proves, yet again, that we can and will take the strongest possible action against those seeking to benefit from Russian connections," Shapps added.
– Amanda Macias
Rescuers work at a site of a regional administration building hit by cruise missiles in Mykolaiv, a city in southern Ukraine.
Editors Note: Images may contain graphic content
— Getty Images / Reuters
Secretary of State Antony Blinken said the U.S. has not seen indications that cease-fire talks between Ukraine and Russia are progressing.
"I've not seen anything that suggests that this is moving forward," the nation's top diplomat said during a press conference in Morocco when asked about Russia's claim that it will reduce military operations near Kyiv. He added that the U.S. still sees significant Russian military campaigns throughout Ukraine.
"I will leave it to our Ukrainian partners to characterize whether there is any type of progress and whether Russia is engaging meaningfully," Blinken said.
"There is what Russia says and there's what Russia does, we are focused on the latter," he added.
– Amanda Macias
Ukrainian negotiators involved in ceasefire talks with Russian representatives said they want to establish an international agreement under which other nations would guarantee Ukraine's security.
David Arakhamia, a member of Ukraine's delegation, pushed for an international security guarantee that would operate in a similar way to NATO's Article 5, where an attack against one member country is viewed as an attack against all members.
He said guarantor countries could include United Nations Security Council member states – the U.S., United Kingdom, China, Russia and France – as well as other countries like Turkey, Canada, Germany, Italy, Poland and Israel. He added that other countries that wish to join will have the opportunity to do so.
Arakhamia said the agreement, which will not include Donbas or Crimea, must first be approved in a referendum by Ukrainians and then ratified by the parliaments of Ukraine and the guarantor countries.
– Amanda Macias
President Joe Biden will host a secure call with the leaders of the "Big 4" most developed nations in Europe to discuss developments in Ukraine. He will speak with President Emmanuel Macron of France, Chancellor Olaf Scholz of Germany, Prime Minister Mario Draghi of Italy and Prime Minister Boris Johnson of the United Kingdom.
The White House announced the call had been added to Biden's schedule less than an hour before the scheduled start time.
The meeting comes shortly after a Russian negotiator, Alexander Fomin, claimed that the Kremlin has "decided to drastically, at times, reduce military activity" around the Ukrainian capital of Kyiv and northern city of Chernihiv.
"We proceed from the fact that the relevant basic decisions will be made in Kyiv and conditions should be created for further normal work," Fomin said, according to an NBC translation. "The General Staff of the Russian Armed Forces will report in more detail upon the return of our delegation to Moscow."
— Christina Wilkie
Russia's deputy defense minister claimed Moscow has decided to "drastically" cut back its military activity near Ukraine's capital.
Alexander Fomin, who spoke following negotiations in Instabul, said Russia would slow its military operations near Kyiv and Chernihiv in order for peace talks to progress. Russia has previously claimed that it would reduce military operations in other parts of Ukraine but then continued its advance.
Fomin added that the Russian Ministry of Defense will give further details "upon the return of our delegation to Moscow."
Growing hope for a ceasefire appeared to boost investor sentiment, as Dow Jones Industrial Average futures rose 200 points or 0.6%. S&P 500 futures also climbed 0.6%, while Nasdaq 100 futures climbed 0.7%.
The price of U.S. benchmark West Texas Intermediate crude oil, which spiked on the heels of Russia's invasion of Ukraine, fell more than 4% to $100 per barrel.
– Amanda Macias
Ukraine's largest airline tells customers that flights will be suspended through at least May 31 as Russia's attacks on the country continue. Ukraine International Airlines had previously scrapped all flights through April 15.
"Given the difficult situation under martial law, the air carrier draws attention to the possibility of forced delays and feedback complications on the service channels of communication with passengers and counts on understanding," the carrier said.
The war has closed the airspace over Ukraine. Reciprocal sanctions with Russia have meant longer flights as airlines avoid Russian airspace and vice versa and roiled the aviation market with hundreds of foreign-owned planes stuck in the country.
— Leslie Josephs
Members of the Ukrainian Volunteer Corps fight against Russian troops in the southeastern Zaporizhzhia region.
— Reuters
Three humanitarian corridors have been opened in Ukraine on Tuesday, according to Deputy Prime Minister Iryna Vereshchuk.
The corridors will allow civilians to evacuate from the cities of Melitopol and Mariupol, with two separate routes operating in the latter to allow evacuations via government-run buses or private transport.
It comes after no humanitarian corridors were opened on Monday, with Ukrainian officials saying they feared a Russian attack on evacuation routes was looming.
— Chloe Taylor
Maksym Kozytskiy, governor of Ukraine's Lviv region, said Tuesday that Ukraine's air defense systems had shot down three missiles over the district of Zolochiv — around 65 kilometers (40 miles) east of the city of Lviv.
Kozytskiy said there was no threat to residents of the Zolochiv district and that no one was hurt in the incident.
Lviv, a city in western Ukraine, had until recently avoided being the scene of active hostilities, with many Ukrainians settling there after fleeing conflict zones elsewhere in the country. According to Kozytskiy, more than 257,000 Ukrainians have resettled in the Lviv region since the beginning of the war.
— Chloe Taylor