President Donald Trump listens to a question Wednesday during a meeting with German Chancellor Angela Merkel during the NATO summit at The Grove in Watford, England. Credit: Evan Vucci | AP

As dignitaries and world leaders milled Tuesday around Buckingham Palace at a NATO summit reception, Canadian Prime Minister Justin Trudeau, British Prime Minister Boris Johnson and French President Emmanuel Macron chatted in a loose circle.

Snippets of their conversation rose above the din and were captured in a short video that went viral after viewers surmised that the group appeared to be joking about President Donald Trump’s performance earlier in the day.

“Is that why you were late?” a smiling Johnson asks Macron in the 25-second clip first shared by the Canadian Broadcasting Corp.

“He was late because he takes a 40-minute press conference off the top,” Trudeau chimes in.

While answering questions during a press briefing Wednesday, Trump responded to the video by lobbing an insult — buffered by a compliment — at Trudeau.

“Well, he’s two-faced,” Trump said of the Canadian leader. “Honestly with Trudeau, he’s a nice guy. I find him to be a very nice guy. But the truth is that I called him out on the fact that he’s not paying 2 percent and I guess he’s not very happy about it.” He continued: “It’s Canada, they have money, and they should be paying 2 percent, so I called him out on that and I’m sure he wasn’t happy about that but that’s the way it is. Look, I’m representing the U.S. and he should be paying more than he’s paying and he understands that. So I can imagine he’s not that happy, but that’s the way it is.”

Hours before the reception, Trump had turned what were “expected to be brief photo opportunities” with NATO Secretary General Jens Stoltenberg, Macron and Trudeau into “his own personal daytime cable show,” The Washington Post reported. During the one-on-one meetings, Trump clashed with Macron and needled Trudeau over Canada’s NATO spending.

“Trump pronounced, prodded and pushed America’s allies into a state of unbalance — seizing the global stage to both bully and banter, all while keeping himself at the center of attention,” The Post’s Ashley Parker, Philip Rucker and Michael Birnbaum wrote, noting that the three impromptu news conferences ended up spanning two hours.

At the Tuesday evening reception hosted by Queen Elizabeth II inside the palace’s Green Drawing Room, none of the three leaders — who appeared unaware they were on camera — mentioned Trump by name.

After Trudeau’s comments, Macron can be seen replying inaudibly and gesturing.

“You just watched his team’s jaws drop to the floor,” an animated Trudeau later tells the group.

Suggestions that Trump’s behavior was the subject of the leaders’ conversation sparked pointed commentary and derision on social media. By early Wednesday, the video, which reportedly came from a CBC journalist who caught the moment on a TV pool feed, had been watched nearly 5 million times.

For decades, Trump has publicly expressed concern that the United States is a “laughing stock,” as he tweeted in 2015. The Post found in 2016 that Trump had stated some variation of the criticism at least 103 times going back as early as 1987. During his presidential campaign, Trump repeatedly vowed to change that perception if elected.

Then, as Trump addressed the U.N. General Assembly last year, he was visibly caught off guard when his remarks were met with an unexpected response — laughter.

Trump had just boasted “that his administration had accomplished more over two years than ‘almost any administration’ in American history, eliciting audible guffaws” from members of the audience, which included a number of world leaders, The Post’s David Nakamura reported at the time.

“Didn’t expect that reaction,” Trump said, drawing more chuckles, “but that’s OK.”

Later, the president reportedly insisted that his statement “was meant to get some laughter,” adding, “It was great.”

Trump has yet to publicly address Tuesday’s video, tweeting early Wednesday only that he “enjoyed” his post-reception meeting with Johnson at 10 Downing Street, where the pair “talked about numerous subjects including @NATO and Trade.” The White House did not respond to a request for comment.

The three leaders in the video have been equally silent.

When Trudeau arrived at the summit early Wednesday, he walked briskly by reporters and did not answer shouted questions regarding his remarks allegedly about Trump. Later, as leaders sat down for their meeting, Trudeau could be seen going over to Trump and shaking his hand politely. The two men said something quickly to each other, then Trudeau walked away. Johnson’s office declined to comment to The Post, and representatives for Macron could not be reached.

Meanwhile, social media was flooded with reactions.

Some viewers were shocked to witness the leaders seeming to act like “mean girls,” as one person put it.

“Oh my God,” a Twitter user wrote. “This is quite something,” another person opined.

Others quickly noticed that a member of the royal family was also involved in the exchange, identifying Princess Anne, the daughter of Queen Elizabeth II. A photograph taken at the reception showed the princess talking to Trudeau and Johnson. Earlier in the evening, Anne was seen in another viral video appearing to shrug off a “scolding” from the queen for not joining the royal receiving line to greet the president and first lady.

Several people warned that Trump would probably retaliate if he saw the leaders appearing to laugh at his expense.

“Trump is watching this somewhere and drafting orders to invade Canada,” tweeted Robyn Urback, a Globe and Mail columnist. “These last 150ish years have been fun, friends.”

“Oh, man, Trump’s going to start World War III over this,” Chicago Tribune humor columnist Rex Huppke wrote.

Still, not everyone perceived the video as a negative reflection of Trump or the United States.

“This is great news for Trump,” Fox News host Laura Ingraham tweeted. “Foreign leaders have been laughing at Republican presidents since Reagan.”

Washington Post writer Michael Birnbaum contributed to this report.