Boris Johnson has said Vladimir Putin threatened him with a missile strike in an "extraordinary" phone call in the run-up to Russia's invasion of Ukraine.
The then-prime minister said Mr Putin told him it "would only take a minute".
Mr Johnson said the comment was made after he warned the war would be an "utter catastrophe".
The claim is made in a BBC documentary on Mr Putin's interactions with world leaders over the years. The Kremlin spokesman said it was a "lie".
Mr Johnson warned Mr Putin that invading Ukraine would lead to Western sanctions and more Nato troops on Russia's borders.
He also tried to deter Russian military action by telling Mr Putin that Ukraine would not join Nato "for the foreseeable future".
But Mr Johnson said: "He threatened me at one point, and he said, 'Boris, I don't want to hurt you but, with a missile, it would only take a minute' or something like that. Jolly.
"But I think from the very relaxed tone that he was taking, the sort of air of detachment that he seemed to have, he was just playing along with my attempts to get him to negotiate."
President Putin had been "very familiar" during the "most extraordinary call", Mr Johnson said.