“This bellicose intent towards a sovereign democratic country is completely unacceptable and we condemn it in the strongest possible terms,” Mrs Truss wrote on Twitter. “The UK and our allies will continue to expose Russian subterfuge and propaganda and call it out for what it is.”

It is unusual for the US to go public with such specific intelligence determinations, but the Biden administration has decided to try to pre-empt any Russian claims of Ukrainian belligerence by exposing an alleged strategy of sabotage and disinformation.

The Pentagon spokesman John Kirby said the US wanted the world to know how an invasion could play out, because this scenario was from the same playbook the Russians used in Crimea in 2014.

Russia, which backs President Bashar al-Assad’s regime, carried out a large-scale disinformation campaign in Syria.

Moscow repeatedly tried to link civil defence rescuers, the White Helmets, to chemical weapons attacks, alleging they were preparing “false flag” attacks that would provoke the West into attacking the Syrian government.

Russia accused the US on Thursday of ramping up tensions and ignoring Moscow’s calls to ease a standoff over Ukraine, a day after Washington announced it would send nearly 3,000 extra troops to Poland and Romania.

Russia has massed more than 100,000 troops on the Ukrainian border and Western countries say they fear Moscow may be planning to invade.

Jens Stoltenberg, Nato Secretary-General, said there had been a significant movement of Russian military forces into Belarus in recent days.

“This is the biggest Russian deployment there since the Cold War,” he said, adding that the expected deployment includes 30,000 combat troops, Spetsnaz special operations forces, SU-35 fighter jets, S-400 air defence systems and nuclear-capable Iskander missiles.

Kremlin spokesman Dmitry Peskov denounced the US troop deployments on a conference call with reporters on Thursday.

“It’s obvious that these are not steps aimed at de-escalating tensions, but on the contrary they are actions that lead to increasing tension,” he said. “We constantly call on our American counterparts to stop aggravating tensions on the European continent. Unfortunately, the Americans continue to do so.”

Western powers have been engaged in intense diplomatic efforts – coupled with the threat of sanctions against Putin’s inner circle – to deter what they fear to be a looming invasion

Olaf Scholz, Germany’s Chancellor, announced he would soon travel to Moscow to discuss the crisis, while France’s President Emmanuel Macron raised the prospect of a visit.

Meanwhile, Russia said yesterday it is closing the Moscow bureau of German broadcaster Deutsche Welle and revoking staff accreditations in Russia, in response to Berlin’s ban on the German-language channel of Russian state TV network RT.

Deutsche Welle called the decision “absurd” and a “complete overreaction”.

The German government said the move was unacceptable and had “no basis of comparison whatsoever” with Berlin’s ruling on RT.

“I urgently appeal to the Russian side not to abuse RT’s licensing problems for a political reaction,” Germany’s Culture Minister Claudia Roth said.