Vladimir Putin has made more than 30 nuclear threats since Russia invaded Ukraine, Boris Johnson has said.
Speaking to LBC's Nick Ferrari, in an interview that will air at 7am tomorrow, the Prime Minister said a peace agreement to end the war was possible, however.
Asked how many threats to deploy nuclear weapons, the Prime Minister accused Moscow of "sabre rattling", saying: "There's an analysis that I think has been done by somebody recently, a think tank, that they’re looking at about 35 mentions or perhaps it's a little bit more now, of that issue.
"But I think it's very, very important that we shouldn't allow ourselves to be side-tracked by this kind of sabre-rattling, because fundamentally, what Putin is trying to do is to reframe this. It's about Russia versus NATO.
"It's about a stand-off of that kind. It's not. It's about his attack on an entirely innocent country, with conventional weapons, with artillery, bombardments with planes, shells and so on.
"And it's about the Ukrainians’ right to protect themselves. That is what this is about, and what we had today, at NATO, was yet again, the Alliance being tested, being asked, being interrogated.
"Are we resolved? Are we determined? Will we give the Ukrainians the means to protect themselves? And the answer was absolutely yes and, if anything, the strength of the unity is greater than it was before."
It came as the PM attended the NATO summit in Madrid as the defensive alliance met to talk about the invasion.
Mr Johnson this week announced a further £1bn to support the Ukrainian military effort.
The PM said Mr Putin could negotiate an end to the conflict, adding: "The Russian president actually enjoys very considerable levels of public support in Russia… depending on how you measure these things.
"He has a considerable margin of manoeuvre, to say 'look, I went in, I had to achieve certain things', and it will be up to him to specify what he thought that those were.
"'But in the interests of peace, in the interests of the world, the time has come to bring the technical military operation to an end, and to withdraw and to seek a new arrangement' [Putin could say].
"That is what I think he should do."
