The Pentagon said Thursday that it had seen signs some Russian troops were withdrawn from the Ukrainian border over the last 24 hours.
"We've seen some Russian forces move off the border," said Pentagon spokesman Army Col. Steve Warren.
Warren, though, cautioned that "it's too early to tell what it all means," noting that there were "tens of thousands" of troops in position. He said Russia still held "a tremendous amount of combat power arrayed along the Ukrainian border."
Warren said the remaining Russian forces are still "capable of even offensive military operations should they choose to do so."
NATO Commander Gen. Philip Breedlove, though, expressed skepticism on Twitter about the Russian withdrawals on Thursday.
"Verified and complete withdrawal of Russian troops from the Ukraine border will do much to deescalate the situation," he tweeted.
"Russian troop withdrawal will not erase recent events or slow @NATO's adaptation to the new security environment in Europe," he added.
Russian President Vladimir Putin on Monday said he had ordered the troop pull back, but the White House has been skeptical, saying it would welcome efforts to de-escalate the crisis over Ukraine, but called for proof.
The U.S. is continuing to show its support for the government in Kiev, sending the Ticonderoga-class guided missile cruiser USS Vella Gulf to the Black Sea.
The cruiser, which will arrive on Friday, will conduct training and security engagements with allies and partners, Warren said.
The deployment comes as Ukraine is preparing to conduct presidential elections on Sunday.