ritain’s armed forces minister said on Monday he feared a Russian attack on Ukraine was now “very imminent”.
James Heappey stressed that “minutes” after Vladimir Putin had given the order, missiles could be hitting Ukraine.
He emphasised that the Russian president had now deployed all the military assets needed for an invasion which could be launched with no “notice”.
He also cast doubt on whether the deployment of at least 130,000 troops around Ukraine’s borders was part of a “coercive diplomacy” strategy.
He told Sky News: “My nervousness is if this was indeed just a play by Vladimir Putin to get a seat at the negotiating table, he had that when he had 50,000 troops on the border of Ukraine.
“But he has kept on building them up. My fear is that it is now very imminent.
“That is not to say that it is definitely going to happen. I hope that diplomacy can win through.”
He also told Britons in Ukraine to leave now while commercial flights and motorways are still usable.
Mr Heappey added: “This isn’t a warning about something which could happen in three months time. This is a warning because minutes after Putin gives the order missiles and bombs could be landing on Ukrainian cities and that means British citizens should leave now while they have the opportunity.”
Boris Johnson was joining last-ditch diplomatic efforts on Monday to bring Mr Putin “back from the brink” of war, holding talks with world leaders before a trip to Europe during this week’s “window of opportunity” for de-escalation. German Chancellor Olaf Scholz is due to travel to Moscow to meet Mr Putin on Tuesday.
But in an effort to reduce tensions Ukraine’s ambassador to the UK said on Sunday the country could consider dropping its ambition to join Nato to avoid war.
Vadym Prystaiko told BBC Radio 5 that the country, which he said was being threatened and blackmailed, would consider “serious concessions” including removing the goal of joining the Nato alliance from the Ukrainian constitution.
Mr Prystaiko also warned that the panic being caused by the West sounding the alarm could be playing into Mr Putin’s hands as he rebuked Defence Secretary Ben Wallace over his remarks that there was a “whiff of Munich in the air” – seen as a dig at European allies over appeasing Russia.
“It’s not the best time for us to offend our partners in the world, reminding them of this act which actually not bought peace but the opposite, it bought war,” Mr Prystaiko said.
A source close to Mr Wallace explained that his frustrations centred on if Mr Putin strikes “come what may, then all the diplomacy would have been a straw man”, rather than being aimed at any European allies.
US President Joe Biden held talks with Ukrainian President Volodymyr Zelensky on Sunday, vowing that the US and allies would “respond swiftly and decisively” in the event of any further Russian incursion.
But Mr Zelensky has sought to play down the threat over the weekend, saying: “The best friend of our enemies is panic in our country. And all this information is just provoking panic and can’t help us.”
Moscow denies it is planning an invasion and Russian Foreign Ministry spokeswoman Maria Zakharova accused the White House of stoking “hysteria” but US intelligence suggests the Kremlin could fabricate a “false flag” pretext to attack.
Western leaders have threatened Moscow with a damaging package of sanctions in the event of a further incursion into Ukrainian soil.
Ukraine is not a Nato member and allies in the defence alliance have said they would not join fighting in Ukraine but have bolstered forces in neighbouring nations and are threatening widespread sanctions.