US President Donald Trump (left), and Justin Trudeau, Canada's Prime Minister, walk in to the West Wing of the White House in Washington DC on June 20, 2019.

US President Donald Trump called Justin Trudeau "two-faced" after the Canadian Prime Minister appeared to be caught on camera joking about his press appearances during a chat with other leaders at a NATO summit in Britain.

Trudeau was filmed at a Buckingham Palace reception on Tuesday describing how surprised US officials appeared to be by Trump's performance at an earlier press.

"...It was like a 40-minute press conference," Trudeau said, "Forty minutes."

Trudeau added with a chuckle: "I just watched his team's jaws drop to the floor."

"That was funny when I said the guy's two-faced," Trump was caught saying on an audio clip following a lunch with some NATO leaders.

At a final news conference, Trudeau played down the incident, saying he and Trump had enjoyed a great meeting and that the jaw-dropping comment was a reference to the announcement of the location of the next meeting of G7 leaders at the US presidential retreat, Camp David.