The US has ordered the relatives of its embassy staff in Ukraine to leave amid rising tension in the region.
The State Department has also given permission for non-essential staff to leave and urged US citizens in Ukraine to consider departing.
In a statement, it said there were reports that Russia is planning significant military action against Ukraine.
Russia has denied claims that it is planning to invade Ukraine.
The State Department also warned people not to travel to Ukraine and Russia due to the ongoing tension and “potential for harassment against US citizens”.
“There are reports Russia is planning significant military action against Ukraine,” an advisory from the State Department said.
A State Department official told the AFP news agency that the embassy remains open but repeated warnings from the White House that an invasion could come at “any time”.
They said that the government “will not be in a position to evacuate US citizens in such a contingency”.
The move by the US is part of a series of precautions the State Department employs when crises could put American diplomats in harm’s way, the BBC’s Barbara Plett Usher reports.
