Boris Johnson has said the UK will “contribute” to any NATO deployments if Russia invades Ukraine.
The prime minister insisted Britain and its allies will not “bargain away” the vision of a free Europe.
He told MPs: “If Russia invades Ukraine, we would look to contribute to any new NATO deployments to protect our allies in Europe.
“We cannot bargain away a vision of a Europe whole and free that emerged in those amazing years of 1989 to 1991.
“We will not reopen that divide by agreeing to overturn the European security order because Russia has placed a gun to Ukraine’s head.”
He added: “There is nothing new about large and powerful nations using the threat of brute force to terrify reasonable people into giving way to otherwise completely unacceptable demands.”
The prime minister said Western allies will act “in unison” to any Russian attack on Ukraine, imposing sanctions “heavier than anything we have done before”.
But foreign secretary Liz Truss told MPs a scenario in which the UK would send troops to defend Ukraine is “unlikely”, according to PA news agency.
Meanwhile, Johnson insisted he and the Tory government are “100 per cent focused on dealing with people’s priorities, including the UK’s leading role in protecting freedom around the world”.
He said the UK has supplied anti-armour missiles and further training to Ukrainian troops.
But reflecting on what would happen if Russia did attack Ukraine, Johnson said: “I shudder to contemplate the tragedy that would ensue.
“Ukrainians have every moral and legal right to defend their country and I believe their resistance would be dogged and tenacious, and the bloodshed comparable to the first war in Chechnya, or Bosnia, or any other conflict that Europe has endured since 1945.
“No-one would gain from such a catastrophe.
“Russia would create a wasteland in a country which as she constantly reminds us, is composed of fellow Slavs; and Russia would never be able to call it peace.”
Previously, the death toll from the Bosian war was estimated at around 100,000, and the two Chechnyan wars at approximately 160,000.
The prime minister said the UK has been collaborating with the US and European allies for months in order to prevent a war, using dialogue and sanctions as deterrence.
Johnson said that last month, he spoke to Russia’s president Vladimir Putin and told him NATO “had no thought of encircling or otherwise threatening his country”, but that Ukraine “of course enjoys an equal and symmetrical right to that of Russia”.
But Putin has made clear he sees Ukraine’s desire to become a NATO member and NATO’s open-door policy as a threat to Russia’s borders and security.
According to Russian news agency TASS, Russia also demands that NATO withdraws foreign troops, weapons and equipment from Bulgaria and Romania.
In May 1997, Moscow and the Western-led NATO agreed they “do not consider each other as adversaries”, but Nato has been expanding closer and closer to Russia ever since – with Hungary, Poland and the Czech Republic joining NATO in 1999, followed by Bulgaria, Latvia, Lithuania, Romania, Slovakia, Slovenia and Estonia in 2004, Albania and Croatia in 2009, Montenegro in 2017 and North Macedonia in 2020.
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