As the impeachment inquiry heats up in Washington, with the House Judiciary Committee set to hold its first public hearing Wednesday, President Trump has found himself in tense moments with fellow world leaders at the North Atlantic Treaty Organization summit in London.

The leaders, who are celebrating the 70th anniversary of the transatlantic alliance, are meeting Wednesday at a golf resort outside of London to discuss threats including terrorism, arms control and China.

But tension among the leaders of NATO member countries over the alliance's role also appears to pose a threat to the partnership.

While the leaders of the 29-member NATO alliance were all smiles as they posed for the ceremonial family photo Wednesday, Mr. Trump and the United States' closest allies had some awkward moments Tuesday, reports CBS News' Paula Reid.

While meeting with Canadian Prime Minister Justin Trudeau, Mr. Trump said Canada is "slightly delinquent" in its contribution to NATO.

Hours after the bilateral meeting between Mr. Trump and Trudeau, the Canadian prime minister, alongside British Prime Minister Boris Johnson and Macron, appeared to mock the U.S. president during a reception at Buckingham Palace.

"He was late because he takes a 40-minute press conference off the top," Trudeau can be heard saying, adding that "you just watched his team's jaws drop to the floor."

French President Emanuel Macron and Mr. Trump engaged in a tense exchange over Syria, with Macron telling the president, "The first burden we share, the first cost we pay, is our soldiers' lives."

"Would you like some nice ISIS fighters?" Mr. Trump replied. "I could give them to you."

Macron told the president his "number one problem are not the foreign fighters. It's the ISIS fighters in the region."

The response from the French president led Mr. Trump to declare that his response was "one of the greatest non-answers I've ever heard."

Mr. Trump canceled his scheduled news conference via Twitter, "because we did so many over the past two days."

Mr. Trump has in the past criticized NATO, calling it "obsolete" and demanding the other members of the alliance pay more. But in London, the president has embraced the partnership, even as he cast doubt on whether the U.S. would defend a nation that does not spend the agreed-upon 2% of GDP on defense.

Mr. Trump answered questions from reporters for a combined two hours Tuesday during meetings with Macron, Trudeau and NATO Secretary General Jens Stoltenberg.

On Wednesday, Mr. Trump met with German Chancellor Angela Merkel and hosted a lunch with NATO members who have met their financial commitments.