The US State Department has urged Americans currently in Ukraine to leave the country "now", citing what it said was "increased threats of Russian military action" against Kiev.
"Do not travel to Ukraine due to the increased threats of Russian military action and Covid-19; those in Ukraine should depart now via commercial or private means," read an updated advisory posted on the State Department's website.
The US has been releasing intelligence which it claims is proof that Russia is prepared to mount a military aggression against Ukraine any time now, but Moscow has accused Washington of "hysteria" over tensions near KIev.
Direct engagements between the US and Russia have yielded little substantial progress, with the Kremlin saying the White House failed to address its key security concerns.
Multiple media outlets reported that President Joe Biden will speak to his Russian counterpart Vladimir Putin over telephone on Saturday, moving up a Kremlin-proposed schedule from February 14.