“We ordered the departure of most of the Americans still at the US embassy in Kiev. The risk of Russian military action is high enough and the threat is imminent enough that this is the prudent thing to do,” Blinken told a news conference in Honolulu.

Most embassy staff were ordered to leave Ukraine immediately due to the threat of an invasion by Russia, with the department saying it appeared increasingly likely that the situation headed towards “some kind of active conflict”.

This added to the State Department’s call earlier this week for private US citizens to leave Ukraine immediately.

US warnings that the Russian buildup of more than 100,000 troops on Ukraine’s borders could herald an invasion have become increasingly urgent in recent days.

Moscow has denied its plans to invade, branding the US warnings “hysteria” and saying it has its own security concerns over what it terms aggression by Nato allies.

Speaking after meeting his Japanese and South Korea counterparts, Blinken reiterated that a diplomatic solution remained possible and the way to pursue that was for Moscow to de-escalate.

“The diplomatic path remains open. The way for Moscow to show that it wants to pursue that path is simple. It should de-escalate, rather than escalate,” Blinken said.