Russia-Ukraine updates: Putin suspends key US-Russia nuclear treaty

White House press secretary Karine Jean-Pierre talked about the latest developments in Ukraine and slammed Russia over its missile strike on the apartment building in Dnipro.

"This weekend’s strikes are another example, as you've heard us say, of the brutal and barbaric war that Russia is waging against the Ukrainian people,” she told reporters during a White House press briefing.

“And we have seen this over and over again," she added.

Jean-Pierre also praised the UK’s announcement Monday that it plans to send Challenger 2 tanks to Ukraine.

The press secretary didn't say whether the U.S. would provide tanks to Ukraine or if Biden would pressure other countries to do so.

She noted that Defense Secretary Lloyd Austin was going to host another multinational meeting on Friday of the "Ukraine Contact Group" -- a gathering of defense ministers to discuss security assistance to Ukraine.

-ABC News' Ben Gittleson

Kyiv's infrastructure could collapse at any second as Russia's sporadic missile attacks along with freezing winter temperatures put local authorities under increasing strain, the city's mayor Vitali Klitschko told Reuters.

"It's pretty cold in Ukraine right now so living without electricity and heating is almost impossible. The situation is critical. We are fighting to survive," he told Reuters.

Klitschko, who is attending World Economic Forum annual meeting in Davos, pleaded with allies to speed up deliveries of air defense systems.

"We don't talk about the collapse, but it can happen ... at any second (because) Russian rockets can destroy our critical infrastructure in Kyiv," he said.

The death toll from Saturday's missile attack on an apartment building in Dnipro has risen to 45, including six children, according to Borys Filatov, the city's mayor.

The search and rescue operations have ended, according to the emergency services.

In addition to the fatalities, there were 79 people wounded, including 16 children, according to emergency services.

Thirty-nine people were rescued from the rubble, including six children, emergency services said.

-ABC News' William Gretsky

Ukrainian soldiers arrived in the United States on Sunday to begin training on the Patriot air defense missile system at Fort Sill, Oklahoma, a U.S. military official said.

The training at Fort Sill is expected to last several months, and then switch briefly to Europe, officials said.

The U.S. military’s expanded combat training of Ukrainian forces in Germany began Sunday, Gen. Mark Milley, chairman of the Joint Chiefs of Staff, told The Associated Press.

-ABC News' Luis Martinez