The US has ordered the relatives of its embassy staff in Ukraine to leave the country, as fears rise of a Russian invasion.
Non-essential embassy staff have also been told they can leave, and US citizens have been urged to do the same.
The State Department said the embassy remained open, but that a Russian invasion could come “at any time”.
Russia has denied having any plans for military action in 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 were a Russian invasion to happen, the US 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.
It is thought that nothing specific over the past 24 hours triggered the decision.
The head of the military defence alliance Nato has warned there is a risk of fresh conflict in Europe after an estimated 100,000 Russian troops amassed on the border.
Source: BBC