Canada's prime minister is at the centre of international media coverage this morning after his off-the-cuff remarks at the NATO summit were broadcast around the world.

Trudeau is seen chatting at a social event at Buckingham Palace on Tuesday (December 3) with Princess Anne, British prime minister Boris Johnson, and French prime minister Emmanuel Macron.

They appear to be joking and laughing about U.S. president Donald Trump.

The video begins with Johnson asking why the U.S. president didn't show up on time.

"He was late because he takes a 40-minute press conference," Trudeau says with astonishment in the video.

Macron follows with inaudible remarks.

Later in the video, Trudeau says: "I've watched his team's jaws just drop to the floor."

These private remarks contrast with Trudeau's efforts to convey his friendship with Trump on his Twitter feed.

"I met with @POTUS in London today, where we talked about our support for the new NAFTA that will create jobs and opportunities for Canadians & Americans alike," Trudeau declared. "We also discussed how important @NATO and the Canada–U.S. partnership are to peace & security around the world."

Speaking with reporters, Trump described Trudeau as "two-faced".

Then Trump criticized Canada for not devoting two percent of its gross domestic budget to military expenditures.

"And honestly with Trudeau, he's a nice guy. I find him to be a very nice guy," the president said. "But the truth is I called him out on the fact that he's not paying two percent and I guess he's not very happy about it.

"He's not paying two percent and he should be paying two percent," Trump continued. "It's Canada, they have money, and they should be paying two percent."

This two percent figure is often held up by NATO, but in an interview with the Georgia Straight in 2017, author and arms-trade critic Andrew Feinstein called it "meaningless".

That's because two percent of GDP is going to add up to significantly different contributions among NATO alliance members because their economies are so different.

"Unless one is clear on what one is spending the money on and what it is going towards, it's a completely nonsensical approach to the trade," Feinstein said.

He also described the F-35 fighter jets as the "ultimate arms-trade white turkey".

In 2018, Trudeau enraged Trump and two senior members of his administration with his closing remarks at the G7 summit in Quebec.

Trump's senior economic adviser, Larry Kudlow, characterized Trudeau's remarks at that time as a "betrayal".

U.S. trade representative Peter Navarro went even further.

"There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door," Navarro told Fox News Sunday.

The U.S. trade representative later apologized.