Russia is massing more troops near Ukraine and an invasion could come at any time, including during this month's Winter Olympics, Washington said on Friday as Moscow further stiffened its response to Western diplomacy.
Commercial satellite images from a private US company showed new Russian military deployments at several sites near Ukraine and, in his starkest warning yet to US citizens, president Joe Biden said he would not send troops to rescue any who remained there in the event of a Russian assault.
Things could go crazy quickly.
"Things could go crazy quickly," Mr Biden told NBC News.
Mr Biden held a phone call on the crisis with the leaders of Britain, Canada, France, Germany, Poland and Romania, as well as the heads of Nato and the EU.
Following that meeting and with alarm spreading, British prime minister Boris Johnson joined a handful of other nations in urging its citizens to leave Ukraine.
He told the meeting that he feared for the security of Europe and stressed the need for "a heavy package of economic sanctions ready to go, should Russia make the devastating and destructive decision to invade Ukraine," his office said.
Moscow, meanwhile, said answers sent this week by the EU and Nato to its security demands showed "disrespect".
Mr Biden met his national security advisers overnight, a source familiar with the meeting said. US officials believed the crisis could be reaching a critical point, with rhetoric from Moscow hardening, six Russian warships reaching the Black Sea, and more Russian military equipment arriving in Belarus, the source said.
"We're in a window when an invasion could begin at any time, and to be clear, that includes during the Olympics," said US secretary of state Antony Blinken. The Beijing Games end on February 20th
"Simply put, we continue to see very troubling signs of Russian escalation, including new forces arriving at the Ukrainian border," Mr Blinken added.
Japan, Latvia, Norway and the Netherlands also told their citizens to leave Ukraine immediately, while Israel said it was evacuating relatives of embassy staff.
Russia has already massed more than 100,000 troops near Ukraine, and this week launched joint military exercises in neighbouring Belarus and naval drills in the Black Sea.
Russia's chief of general staff Valery Gerasimov and his US counterpart General Mark Milley discussed international security in a phone call on Friday, the Interfax news agency said.
Ukraine's sea port authority said Russia had withdrawn previously announced restrictions linked to the naval drills for ships in the Sea of Azov, which links to the Black Sea.
'Impoliteness and disrespect'
Moscow denies planning to invade Ukraine, but says it could take unspecified "military-technical" action unless a series of demands are met, including promises from Nato never to admit Ukraine and to withdraw forces from Eastern Europe.
The West has said those main demands are non-starters. The EU and Nato alliance delivered responses this week on behalf of their member states.
Russia's foreign ministry said it wanted individual answers from each country, and called the collective response "a sign of diplomatic impoliteness and disrespect".
Several Western countries launched diplomatic pushes this week to persuade Russia to back down, but Moscow brushed them off, yielding no concessions to French president Emmanuel Macron, who visited on Monday, and openly mocking British foreign secretary Liz Truss when she came on Thursday.
Four-way talks in Berlin between Russia, Ukraine, Germany and France on Thursday also yielded no progress. Paris and Kyiv said the Russian delegation had demanded Ukraine negotiate directly with the separatists, a "red line" Ukraine has rejected.
Conflicting views
US-based Maxar Technologies, which has been tracking the build-up of Russian forces, said images taken on Wednesday and Thursday showed large new deployments of troops, vehicles and warplanes in western Russia, Belarus and Crimea, which Russia annexed from Ukraine in 2014. The images could not be independently verified by Reuters.
Russia says it has the right to move forces on its territory as it sees fit, and they pose no external threat.
Western countries have mostly stood together in threatening economic sanctions against Russia if it invades, but have given conflicting views on the threat's immediacy.
Washington and London have said invasion could come within days. Mr Macron, by contrast, said he thinks Russia does not have designs on Ukraine and called the existing Franco-German-led peace process for Ukraine's separatist conflict a way out.
Moscow has responded dismissively to Western pressure. Pictures of Mr Macron seated far from Mr Putin at the opposite end of a huge table in the Kremlin went viral on the internet.
Covid test
The Kremlin said on Friday the arrangement had been necessary because Mr Macron had refused a Covid-19 test by Russian doctors.
French officials said Mr Macron's travel schedule left no time to wait for test results; sources also said Macron's office had been worried Moscow would sample his DNA.
A Russian attack on Ukraine could begin any day now and would likely start with an air assault, White House national security adviser Jake Sullivan said on Friday.
Mr Sullivan, speaking at a White House briefing, said any American still in Ukraine should leave in the next 24-48 hours because a Russian air assault would make departures difficult.
He said a rapid assault on the Ukrainian capital, Kyiv, is another potential action Russia could take.
Mr Sullian added that Russia is looking for a pretext to invade Ukraine. He stressed that the White House does not believe Mr Putin has made a final decision.
