French President Emmanuel Macron says his now famous white-knuckle handshake showdown with his US counterpart Donald Trump was "a moment of truth" — designed to show that he's no pushover.

Mr Macron told a Sunday newspaper in France that "my handshake with him, it wasn't innocent".

"One must show that you won't make small concessions, even symbolic ones, but also not over-publicise things, either," he said.

He added: "I don't believe in diplomacy through public criticism but through bilateral dialogue. I don't let anything pass. That is how you get respect."

Mr Macron's office confirmed the veracity of the President's comments in Le Journal du Dimanche.

At their first meeting, ahead of a NATO summit in Brussels on Thursday, the two men barely knew each other, but seemed to have a hard time letting go, locking hands for so long that their knuckles started turning white.

Images from the photo session at the US ambassador's residence in Brussels showed Trump finally giving up, his fingers loosened while Macron is still holding on tightly. Both men's jaws seemed to clench.

Footage from the NATO summit, tweeted by Mr Macron himself, showed the French President approaching a crowd of NATO leaders, headed by German Chancellor Angela Merkel and Mr Trump.

Mr Macron walks down the path heading straight towards Mr Trump, but at the last moment swerves to greet Ms Merkel, the head of the Western military bloc, and other leaders.

Mr Macron finally turns his attention to Mr Trump, who characteristically yanks Mr Macron's arm into a dominating handshake.

Mr Trump pulled Mr Macron's hand so hard that the French President had to use his other arm to set himself free, their second awkward moment that was caught on cameras and went viral in just one day.

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A short history of Trump's awkward handshakes

Mr Macron's determination to dominate the handshake may be a lesson for Ms Merkel, who on a recent visit to the Oval Office tried and failed to get Mr Trump to shake her hand.

Sorry, this video has expired Donald Trump ignores Angela Merkel's suggestion to have a handshake

Or from Japanese Prime Minister Shinzo Abe, who was caught in a long, rigorous handshake.

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Prime Minister Malcolm Turnbull had to overreach to shake the US President's hand in a meeting that was postponed by three hours and came after a testy phone call over a refugee deal between Australia and the US.

"You guys exaggerated that call. That was an exaggeration," Mr Trump said moments later.

Sorry, this video has expired Mr Trump says negative phone call with Mr Turnbull 'fake news' in New York meeting

It seems Canadian Prime Minister Justin Trudeau got off lightly with his "nothing-to-see-here" handshake.

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ABC/AP