The U.S. authorities have rejected the idea of sending Russian "peacekeepers" to Ukraine, White House press secretary Josh Earnest has said.

He said at a briefing in Washington on Wednesday that "it is deeply troubling to hear any discussion of Russian 'peacekeepers' being sent to Ukrainian territory."

"These statements are destabilizing and unhelpful," he said.

Earnest also noted that "Russia should anticipate that any such move would be met with condemnation and result in further economic cost and political isolation."