BRITISH nationals have been urged to leave Ukraine immediately amid reports that the US believes Vladimir Putin has decided Russia will invade the eastern European nation.

Reports say Putin has told the Russian military to prepare for an invasion, which the US expects to happen next week.

Nick Schrifin, defense correspondent for PBS, said numerous Western sources had told him of the information.

“US officials anticipate a horrific, bloody campaign that begins with two days or aerial bombardment and electronic warfare, followed by an invasion, with the possible goal of regime change,” he added.

The news comes as the UK Foreign Office told Brits in Ukraine to “leave now via commercial means while they remain available”.

READ MORE: David Pratt: Truth is already the first casualty as the US and Russia clash over Ukraine

A spokesperson said the travel advice had been updated in order to protect the “safety and security of British nationals”.

The advice comes a day after Joe Biden urged all American citizens to leave Ukraine, saying “things could go crazy very quickly”.

Tory defence secretary Ben Wallace said that Russia could mount an invasion “at any time” and that such a conflict would have “tragic consequences” for both countries.

Following talks in Moscow with his Russian counterpart Sergei Shoigu, Wallace said he had received an assurance the Kremlin was not planning to attack its southern neighbour.

But with 130,000 Russian troops massed along the borders and large-scale military exercises taking place in Belarus, he said they would judge such assurances by Moscow’s actions.

“Currently there’s over 130,000 troops stationed at readiness or exercising – plus warplanes, plus ships into the Black Sea – on the borders of Ukraine and that is an action that is not normal,” Wallace said.

“It is beyond normal exercising therefore we will judge that statement on the evidence.”

His news conference took place as Boris Johnson joined other Western leaders on a conference call organised by US President Joe Biden to discuss the situation in the region.

The National: Vladimir Putin and Emmanuel Macron. The two men seemed to have a different verdict on the success of their talks

Also taking part were French President Emmanuel Macron (above with Putin), German Chancellor Olaf Scholz and Nato secretary-general Jens Stoltenberg, as well as EU leaders Ursula von der Leyen and Charles Michel.

Biden’s national security adviser Jake Sullivan said there is the “credible prospect” of an invasion of some sort taking place before the end of the Winter Olympics on February 20.

He said the Russians are in a position to “mount a major military operation in Ukraine any day now”, which could include a “rapid assault on the city of Kyiv” or on other parts of the country.

Speaking from the White House, Sullivan said Russia could choose “in very short order to commence a major military action against Ukraine” but contradicted reports to say the US does not know whether Putin has made a final decision.

Sullivan further warned there will be no military evacuation of US citizens if Russia invades.

He said: “The president will not be putting the lives of our men and women in uniform at risk by sending them into a war zone to rescue people who could have left now but chose not to.”

The National: Joe Biden

Following a frosty meeting in Moscow on Thursday between Foreign Secretary Liz Truss and her counterpart Sergei Lavrov, Wallace said his discussions with Shoigui had been “frank and constructive”.

While he said that he took the minister’s assurances “seriously”, he admitted that he was less optimistic than he had been previously that there could be a diplomatic solution to the crisis.

He said the current disposition of Russian forces meant they could do “a whole range of actions, including an invasion of a neighbouring country, at any time”.

“I was clear about the tragic consequences that any invasion of Ukraine could have for all people – both Ukrainian [and] Russian – and the security of Europe,” he said.

“I think we have had a constructive and frank discussion and I hope it has contributed to a better atmosphere but also to de-escalation, but there is still considerable way to go between the two of us.”

He said they had he discussed “confidence building measures” as well as the importance of implementing the Minsk Agreement, brokered by France and Germany, which was supposed to end the fighting between the Ukrainian military and Russian-backed separatist rebels in the east of the country.

“I reiterated that, to its very core, Nato is defensive. We are not interested in dividing and ruling Russia. We are not seeking confrontation,” he said.

He said that 2000 anti-tank missile launchers supplied by the UK to the Ukrainian military were purely defensive.

He added: “They’re not strategic, they’re short range. They are designed really for the protection of infantry at short range.

“They in no way would pose a threat to an external state as long as that state did not invade that country.”

Wallace denied reports the UK was planning to send 600 Special Forces troops to Ukraine, saying it had only a small number of military trainers in the country whose presence had been fully declared.