PARIS — They shook hands politely and patted each other on the arm stiffly. Their tight-lipped smiles appeared strained and forced. No cheeks were kissed, no friendly rubs were given, none of the bonhomie of their earlier meetings was on display.

So much for the bromance.

After a promising start, the relationship between President Trump and President Emmanuel Macron of France has soured. By the time they met in Paris on Saturday, the trans-Atlantic alliance that was to be showcased by this weekend’s commemoration of the 100th anniversary of the end of World War I appeared to be fraying instead.

“The honeymoon is well and truly over,” said Mark Leonard, director of the European Council on Foreign Relations. “Trump’s visible contempt for allies over trade and the Iran nuclear deal are humiliating for Macron. There were high hopes of Macron’s charm offensive, but Trump’s actions have shown that it had no policy impact and that it is dangerous for any political leader to tie his reputation to the mercurial mood swings of the American president.”

It did not help on Saturday that Mr. Trump canceled a visit to the Aisne-Marne American Cemetery at the foot of the hill where the Battle of Belleau Wood was fought. Aides cited the rain; the Marines who pilot presidential helicopters often recommend against flying in bad weather. But that did not convince many in Europe who saw it as an excuse and another sign of disrespect.