“The ambassador is not just an ambassador,” Mr. Chalghoumi said. “He is directly linked to the president’s family.”

During Mr. Trump’s first term, Jared Kushner helped engineer the Abraham Accords, agreements under which several Arab countries normalized diplomatic relations with Israel. Unabashedly proud of his son’s achievement, the ambassador gives visitors signed copies of his son’s memoir, “Breaking History.” Mr. Kushner is cultivating Middle East ambassadors in Paris, he said, in the hope of persuading more countries to join the accords.

One of those envoys, Rabih El Chaer of Lebanon, said that Mr. Kushner had floated a meeting in the United States between Lebanon’s president, Joseph Aoun, and Prime Minister Benjamin Netanyahu of Israel, an old friend of Mr. Kushner’s. When Mr. El Chaer hesitated, he recalled Mr. Kushner telling him, “I am a man of deals.” Mr. El Chaer said he replied, “I come from the Middle East, where we don’t simply skip over history.”

For Mr. Kushner, too, history hangs over this assignment. Next month, he will celebrate the 250th anniversary of American independence with a party at his residence, at which guests will be serenaded by the Italian tenor Andrea Bocelli. Mr. Kushner has renovated the building, an 18th-century villa that was once owned by the Rothschilds and requisitioned by the Nazis during their occupation of Paris.

To fund the repairs, Mr. Kushner said that he had raised $10 million, much of it from the chiefs of France’s largest companies, whom he asked to contribute $250,000. Other diplomats said that such high-dollar donations were unusual, at least before Mr. Trump became president. Mr. Kushner is, he joked, the project’s “site super.”