U.S. President Donald Trump’s rocky relationship with Justin Trudeau hit a boulder Wednesday when the Canadian prime minister was caught on a hot mic criticizing Trump in a conversation with European leaders at the NATO meeting in London.

Trudeau said he was late to the reception at Buckingham Palace Tuesday evening because Trump “takes a 40-minute press conference off the top.” He then subsequently said Trump’s “team’s jaws dropped to the floor” at one point during their bilateral meeting in his conversation with French President Emmanuel Macron, British Prime Minister Boris Johnson and Dutch Prime Minister Mark Rutte and Princess Anne.

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The clip was first posted by the Canadian Broadcasting Corp.

Trump spoke with reporters for more than two hours Tuesday, the first day of the two-day conference. Trudeau told reporters the jaw drop comment referred to Trump’s announcement the June Group of Seven meeting would be held at Camp David.

“Well, he's two-faced,” Trump said after a bilateral meeting Wednesday with German Chancellor Angela Merkel. He explained Trudeau’s remarks as related to Trump’s criticism of Canada’s less than 2% contribution to NATO funding. Each NATO member is supposed to contribute 2% of its gross domestic product to NATO defense spending. Canada contributes about 1.4%.

“He should be paying more than he’s paying,” Trump said. “I called him out on that, and I’m sure he wasn’t happy about it, but that’s the way it is.”

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A miffed Trump canceled a news conference at the end of the NATO summit, saying he had answered enough questions. Trump later was caught on audio saying, “That was funny when I said that guy was two-faced.”

Trudeau dismissed the impact of the gaffe, saying Canada’s relationship with the United States is “extremely strong.”

In a three-hour closed-door session among the 29 NATO members, Trump listed a number of grievances mainly concerned with funding but made not threats, the Washington Post reported. Trump was to lunch with representatives of countries meeting the 2% funding goal: Greece, Britain, Estonia, Romania, Lithuania, Latvia and Poland. The United States contributes 3.42%.

The incident was the latest sniping incident between Trump and Trudeau. Last year, Trump called Trudeau “very dishonest and weak” in a dispute over steel and aluminum tariffs.

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Trump’s attendance at the summit at the Grove, a country resort in Hertfordshire near London, produced a number of a statements at odds with his past positions. He defended the 70-year-old alliance against Macron’s remarks that it was “brain dead” under current U.S. leadership even though he has repeatedly criticized NATO as having outlived its usefulness.

Trump clashed with Macron on Tuesday as the French leader challenged the U.S. president’s handling of Turkey’s incursion into Syria and his vision for NATO.

He also embraced climate change, saying it was an issue close to his heart, even though in the past he has called it a “hoax” promoted by China and pulled the United States out of the Paris climate accord as one of his first official acts.