President Emmanuel Macron of France struck a chummy tone with President Trump even as he corrected him with a smile during joint appearances on Monday. That one-two punch of flattery and gentle resistance is an example of how some European leaders are trying to approach America at a fraught moment.

The question is whether it will work.

Mr. Macron called Mr. Trump “Dear Donald” four times during a joint news conference on Monday, while emphasizing the shared history between France and the United States — and underscoring that the two leaders had made progress in discussing a sustainable and strong peace agreement for Ukraine.

But even as he stuck to the script and emphasized shared goals and values, Mr. Macron showed himself willing to push back.

When Mr. Trump claimed in the Oval Office that Europe would “get their money back” because of the way they have funded support for Ukraine, Mr. Macron interjected, in a friendly tone, saying, “We provided real money.” And later, in an interview with Fox News before returning to France, Mr. Macron mildly criticized threats to slap tariffs on European consumer goods as counterproductive. “How do you want us to increase security and defense expenditures if we are in a trade war?” he asked.

Europe faces a towering challenge as the full-scale war in Ukraine enters its fourth year and American support for the conflict — and for the continent as a whole — wavers.