Boris Johnson has called on Vladimir Putin to step back from “the edge of a precipice” as he warned that Russia could invade Ukraine at any moment.
The prime minister said the “evidence is pretty clear” that Moscow was planning to attack Ukraine but said there was still time for Putin to think again.
Russia has amassed an estimated 130,000 troops on its border with Ukraine amid reports that the invasion could happen as soon as tomorrow.
Johnson said the amassing of troops was just one element of the “serious preparations” Russia was undertaking.
“This is a very, very dangerous, difficult situation, we are on the edge of a precipice but there is still time for president Putin to step back,” he told reporters on a visit to Scotland.
Western nations have warned Moscow that they will impose heavy economic sanctions if an attack takes place in a bid to halt an invasion similar to Russia’s annexation of the Crimean peninsula in 2014.
Johnson said the world “needs to learn the lesson of 2014” when, he said, not enough was done to move away from Europe’s dependence on Russian gas and oil.
He referred specifically to the Nord Stream 2 gas pipeline project connecting Russia to Germany, saying: “What I think all European countries need to do now is get Nord Stream out of the bloodstream.”
“Yank out that that hypodermic drip feed of Russian hydrocarbons that is keeping so many European economies going,” he said.
“We need to find alternative sources of energy … and get ready to impose some very, very severe economic consequences on Russia.”
Johnson’s intervention comes after his defence secretary, Ben Wallace, announced he was cutting short a holiday abroad to deal with the “worsening” situation in Ukraine.
In a sign of the deteriorating situation, the government has urged British nationals to leave Ukraine as soon as possible.
Wallace stirred controversy when he said there was a “whiff of Munich in the air”, in a reference to the agreement that allowed German annexation of the Sudetenland in 1938 but failed to prevent the Second World War.
But Downing Street suggested that was an incorrect characterisation of Western efforts to prevent conflict in Ukraine.
“I think what has been crucial throughout this period has been the united approach that NATO allies have been taking,” the prime minister’s official spokesman said on Monday.
Johnson also said that Ukraine’s aspirations to join NATO — a bugbear of Putin’s — could not be “bargained away”.
“I think it’s very important that we have a conversation, but what we can’t do is trade away the sovereign rights of the Ukrainians who aspire to Nato membership,” he said.
“That’s something that was a massive gain for our world. If you remember what happened in 1990, you had a Europe whole and free, countries could decide their own futures. We can’t bargain that away. It’s for the Ukrainian people.”
Downing Street confirmed that foreign secretary Liz Truss will chair a meeting of the Cobra emergency committee on Monday to discuss the consular response to the Ukraine crisis.