Russia has sent more forces to its border with Ukraine and could launch an invasion at any time, including during the Winter Olympics, US Secretary of State Antony Blinken said on Friday.
He said Washington was continuing to "draw down" its embassy in Ukraine and repeated a State Department call to American citizens in Ukraine to leave the country immediately.
"Simply put, we continue to see very troubling signs of Russian escalation, including new forces arriving at the Ukrainian border," Blinken told a news conference in the Australian city of Melbourne.
"As we've said before, we're in a window when an invasion could begin at any time, and to be clear, that includes during the Olympics."
Russia, which has more than 100,000 troops near Ukraine's borders, denies Western accusations it may be planning to invade its former Soviet neighbor. The Winter Olympics are being hosted by Beijing until Feb. 20.
Britain said on Thursday the "most dangerous moment" in the West's standoff with Moscow appeared imminent, as Russia held military exercises in Belarus and the Black Sea following the buildup of its forces near Ukraine.
The US State Department urged Americans in Ukraine to leave immediately because of what it called increased threats of Russian military action and Blinken said Washington would continue to draw down its embassy.
"We will continue that process and we've also been very clear that any American citizens who remain in Ukraine should leave now," Blinken said.