US President Joe Biden said he spoke with Ukrainian Prime Minister Denys Shmyhal, who was at the White House Thursday morning meeting with US national security adviser Jake Sullivan, along with Ambassador Oksana Markarova, CNN reported.

"We had a good discussion. I talked about what I'm about to tell you about today, as well as he was thanking the American people for their support, understands it's significant, and we talked about keeping everyone together in terms of Europe, European Union and others, in the effort to stop Putin's brutality," Biden said.

Biden said "enormous credit" should be given to agencies on the ground exposing "war crimes."

"It's so clear to the whole world now. Now [Russia has] launched and refocused their campaign to seize new territory in eastern Ukraine, and we're in a critical window now of time where they're going to set the stage for the next phase of this war," Biden continued.

The US and its allies are "moving as fast as possible" to provide weapons to Ukrainian forces to defend their country, he said, announcing another $800 million in military assistance.