"We're seeing a small number now that appears to be moving away from Kyiv, this on the same day that the Russians say they're withdrawing," Pentagon spokesman John Kirby said.

Kirby was speaking just hours after Russian Deputy Defense Minister Alexander Fomin said that Moscow would scale down fighting around Kyiv and the northern city of Chernigiv after progress was made in peace talks held in Istanbul.

"What I can tell you is that the vast majority of the assembled force that we saw against Kyiv is still there," Kirby said. "We've only seen a small number begin to move away from Kyiv, mostly to the north.

"Russia has failed in its objective of capturing Kyiv," the Pentagon spokesman said, but "it does not mean that the threat to Kyiv is over."

"We're not prepared to call this a retreat or even a withdrawal," he said. "We think that what they probably have in mind is a repositioning to prioritize elsewhere.

"We all should be prepared to watch for a major offensive against other areas of Ukraine," he said, adding that there had been "increased offensive activity" by Russian forces in the breakaway Donbas region.

In addition to the Pentagon, the announcement was met with some skepticism by the White House.

"We should be clear-eyed about the reality of what's happening on the ground and no one should be fooled by Russia's announcements," White House Communications Director Kate Bedingfield told reporters.

Asked if there was a schedule being created for sanctions removal in exchange for progress, Bedingfield said: "I don't know that Russian activity at this time necessarily merits a carrot. We have been very focused on the stick."