Boris Johnson has said Europe is at “a very dangerous moment” and stands on “the brink” of a possible war with Russia.
In a speech at the Munich security conference on Saturday the prime minister said an invasion of Ukraine from the east would bring about the “destruction of a democratic state”.
He warned that the world was at “the eleventh hour” to avert a conflict and said any invasion would echo out like “a shock” around the world and encourage other countries to resort to military aggression.
“This is a very dangerous moment in our history. We stand on the brink of what could be a war in Europe,” Mr Johnson said during a meeting with his Ukrainian counterpart ahead of his speech.
“I think it would be an absolute disaster be disaster for Europe, a disaster for Ukraine, and a disaster, certainly for Russia, if there were to be an invasion.
“And I think everybody at this conference wants to stand united in support, and in solidarity with Ukraine.
“And I remember actually, five years ago, I came here to the Munich Security Conference, I said exactly the same thing to your predecessor, or one of your predecessors, and it is more vital than ever. That we, we stand with you.”
Addressing the conference Mr Johnson told an audience: “It is in our collective interests that Russia should ultimately fail, and should be seen to fail.”
“The risk now is that people would draw the conclusion that aggression pays and that might is right. So we should not underestimate the gravity of this moment.”
Amongst world leaders Mr Johnson has been among the most vocal over the Ukraine crisis – a decision that comes as he seeks to move on from domestic anger over alleged lawbreaking in Downing Street during the Covid lockdown.
His visit to Germany this weekend for the Munich security conference comes as the US government claimed an invasion of Ukraine by Russian forces could come within “several days”.
Russia denies it has plans to attack, but has built up an estimated 150,00 troops on its border with Ukraine.
Mr Johnson has previously called the situation in eastern Europe “very grim” but stressed before his departure to Bavaria that “diplomacy can still prevail” if leaders unite.
Russian president Vladimir Putin has insisted that large-scale military exercises with Belarusian forces close to the Ukrainian border are “purely defensive” and do not represent a threat to invade.
The Kremlin said this week it was is withdrawing some of its military presence from the region, but western government say intelligence suggests that 7,000 troops have actually arrived on the border in recent days.
Other apparent causes for alarm include claims of field hospitals and pontoon bridges spotted close to the border.
There has also been increased activity in the separatist-held eastern region of Ukraine, including reports of a major explosion in the centre of the city of Donetsk on Friday.