Donald Trump has branded Canada's Prime Minister "two-faced" after he was one of a group of Nato leaders who appeared to mock the US president at a Buckingham Palace reception.
Mr Trump said he believed Justin Trudeau was upset that he broached the fact that Canada falls short of the Nato target of spending 2% of its GDP on defence.
After calling the Canadian leader "two-faced", Mr Trump told reporters: "Honestly, with Trudeau he’s a nice guy, I find him to be a very nice guy.
"But you know the truth is that I called him out on the fact that he’s not paying 2% and I guess he’s not very happy about it."
Mr Trudeau has since responded to the "gossiping" in a press conference, saying: "Last night I made a reference to the fact there was an unscheduled press conference before my meeting with President Trump."
He added: "And I have had a number of good conversations with the President over the course of this day and yesterday."
In footage recorded on Tuesday night, Mr Trudeau can be seen as part of a huddle apparently gossiping about the US President's unorthodox style, although Mr Trump was not mentioned by name.
The group also included Prime Minister Boris Johnson and Princess Anne.
During the casual chat, as the leaders sipped drinks, Mr Johnson can be heard asking French President Emmanuel Macron: "Is that why you were late?"
Canadian Prime Minister Justin Trudeau says: "He was late because he takes a 40 minute press conference off the top."
Later in the conversation Mr Trudeau adds: "You just watched his team's jaws drop to the floor."
On Wednesday, when Mr Trudeau was asked what he referred to with the "jaws drop" comment, he said: "We were all surprised and also pleased to learn that the next G7 will be at Camp David, I think that was an unscheduled announcement."
During a press conference to close the Nato meeting, Mr Johnson was asked about the alleged gossiping but dismissed it as "nonsense".
A video clip of the chat, filmed as world leaders met ahead of a summit to mark Nato's 70th anniversary, has been viewed millions of times since it was posted online.
It came after Mr Trump branded Mr Macron's comments that Nato is "brain dead" as "very nasty", before the pair met on Tuesday at the US ambassador's residence in London.
Meanwhile, following an evening reception hosted by Mr Johnson at Number 10, a member of the US Secret Service was pictured leaving with a Christmas bauble gifted to leaders.
Each Nato leader was given one of the decorations and invited to hang it from the Downing Street tree.