Tens of thousands could die if Russia launches a full-scale attack on Ukraine, a UK government minister warned today.
Former Army officer James Heappey said Moscow would be "extraordinarily stupid" to go to war with Ukraine but warned it is a "grave possibility."
It came as Moscow has an estimated 126,000 troops gathered at Ukraine’s border for a possible land and sea invasion on its neighbour.
More Russian forces are arriving in Belarus for claimed military exercises, although they could attack from the north.
Armed Forces Minister Mr Heappey said Ukrainians are "ready to fight for every inch of their country,” as 100 British troops trained Ukrainian forces in anti-tank weaponry.
The UK has sent more than 2,000 NLAW anti-tank missiles to Ukraine’s forces to be used against Russian tanks if they break through the frontline.
Mr Heappey said the UK missile supply demonstrated a show of support and warned: "What stands in front of us, what could be weeks away, is the first peer-on-peer, industrialised, digitised, top-tier army against top-tier army war that's been on this continent for generations.
"Tens of thousands of people could die.
"This is not something that people in Moscow should believe to be bloodless. This is not something that the rest of the world should stand by and ignore.
"It's right that all diplomatic avenues are being exhausted, I just hope that as we're on the brink, people in Moscow start to reflect that thousands of people are going to die and that is not something that anybody should be remotely relaxed about."
It comes after Boris Johnson said the UK is doing "everything possible" to support the people of Ukraine in the face of a Russian "disinformation campaign".
The Prime Minister told the Cabinet that Russian President Vladimir Putin "must not be allowed to rewrite the rules" of international relations as tensions continue to mount.
US Secretary of State Antony Blinken is set to meet his Russian counterpart in Switzerland on Friday in a bid to stop hostilities.
A senior State Department official said: "We are now at a point where Russia could launch an attack on Ukraine at any time."