Biden was skeptical when asked about Russian claims that it will scale down operations near Kviv. 

"We'll see. I don't read anything into it until I see what their actions are," Biden said in a news conference with Singapore Prime Minister Lee Hsien Loong. "We'll see if they follow through on what they're suggesting."

Biden added that he had a meeting with NATO allies, and there seemed to be a consensus to wait and see. 

"But in the meantime, we're going to continue to keep strong sanctions. We're going to continue to provide the Ukrainian military with their capacity to defend themselves, and we're going to keep a close eye on what's going on," he said. 

The head of the International Atomic Energy Agency is in Ukraine for talks with government officials to "ensure the safety and security of the country’s nuclear facilities and help avert the risk of an accident that could endanger people and the environment."

At the Chernobyl nuclear power plant, which was taken by Russian forces on Feb. 24, technical staff members who had worked for nearly four weeks were rotated out last week and replaced with other nearby staff.

Agency Director General Rafael Mariano Grossi's visit confirmed that eight of Ukraine's 15 operational nuclear reactors across four sites were operational, including some in Russian-controlled areas. Others were offline for maintenance. 

The IAEA said a "subcritical" nuclear research facility near Kharkiv that was attacked has a "low" amount of nuclear material, too low to trigger any chain reaction. 

Biden spoke to top European leaders by phone Tuesday about the invasion of Ukraine and the consequences their countries will continue to impose on Russia. 

"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. 

The White House also said that the leaders reviewed their efforts to provide humanitarian assistance to millions of Ukrainians, "both inside Ukraine and seeking refuge in other countries."

They also "underscored the need for humanitarian access to civilians in Mariupol' and "discussed the importance of supporting stable energy markets in light of current disruptions due to sanctions."

The leaders on the call included French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Mario Draghi and British Prime Minister Boris Johnson. 

Secretary of State Antony J. Blinken on Tuesday appeared to cast doubt on Russia's pledge to cut back on hostilities in Ukraine.

"There is what Russia says, and there is what Russia does," Blinken said during a diplomatic trip to Morocco. "We’re focused on the latter, and what Russia is doing is the continued brutalization of Ukraine and its people, and that continues as we speak."

Blinken called on Russia to "end the aggression now, stop firing, pull its forces back, and of course engage in talks."

NATO's Supreme Allied Commander Gen. Tod D. Wolters said Tuesday that Russia fired "multiple" hypersonic missiles in Ukraine, with most directed at military targets. 

"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," Wolters said in testimony before the Senate Armed Services Committee. 

Wolters, who also serves as commander of U.S. European Command, did not specify the exact number of hypersonic missiles launched. 

He suggested intelligence on the strikes is still pending, but said most strikes were launched "at specific military targets." 

An expert recently told NBC News that the missiles are "very, very fast and designed to evade missile defenses." 

As Ukrainian troops continue to claw back territory from Russia around Kyiv, Russian soldiers appear to be adjusting their activity and shifting away from the besieged country's capital.

"We're seeing some movement of troops away from Kyiv, which could be an indication of Putin having to adjust his original plan," a White House official said Tuesday. "But no one should read too much into an adjustment — should momentum build, Russia could change its plans again at any moment, or this could just be a regroup."

On Monday, a senior U.S. defense official said Russia was not making any progress, advances or effort toward Kyiv, while last week, U.S. officials said Russia's assault on the capital failed to gain traction as Ukrainian forces were able to roll back Russian troops to the east and stymie them northwest of the city.

A top U.N. official has called on both Russia and Ukraine to investigate videos that appear to show their soldiers mistreating prisoners of war during the conflict in Ukraine.

The government in Kyiv has said it is looking into a video that purports to show Ukrainians shooting Russian prisoners in the legs.

The commander of Ukraine’s army has suggested that the graphic video is a staged act of propaganda. NBC News was unable to authenticate the video.

The Kremlin — whose disinformation efforts have varied as widely a accusing the U.S. of running a network of nonexistent "biolabs" across Ukraine to denying it has launched a war at all — said it is also investigating the video.

Read the full story here.

A Ukrainian police officer sits on a sports car fitted with a heavy machine gun on the back in Mykolaiv, Tuesday.