US President Joe Biden has said he thinks his Russian counterpart Vladimir Putin will "move in" on Ukraine but does not want "full-blown war".
He told a news conference Mr Putin would pay a "serious and dear price" for invading, but indicated a minor incursion might be treated differently.
The White House later stressed any Russian military move would be met with a swift, severe response from the West.
Russia has some 100,000 troops near the border but denies planning an invasion.