But some of those groups, in a separate offensive aided by Turkey, have pushed the Islamic State back from the Turkish border and appear to be on the verge of retaking the city of Al Bab from the extremist group, which Mr. Trump has vowed to defeat. A Pentagon program supports other rebel groups working with Kurdish militias to fight the Islamic State.

“We don’t consider his statements to represent the new U.S. administration stance,” said Bassam Hajj Moustafa, the political spokesman for the Nour al-Din al-Zenki rebel faction, which lost its American support after being deemed too close to Qaeda-affiliated groups.

Mr. Moustafa called Mr. Trump’s statements “a show” tainted by earlier “racist, problematic comments,” adding, “We’re not taking them seriously, and they will be deleted later.”

Frederic C. Hof, a former Obama administration official who has been a vociferous advocate for more robust intervention against Mr. Assad, said it was too early to predict Mr. Trump’s Syria policy — especially since he had more to learn about the conflict.

“No doubt Mr. Trump will learn during the course of his intelligence briefings,” Mr. Hof wrote in an essay published by the Atlantic Council, a Washington policy institute, that Mr. Assad’s “collective punishment policy” and “mass homicide” of opponents drives recruitment for the Islamic State and Al Qaeda. Ending United States support for rebels would only push them closer to Qaeda-linked groups, Mr. Hof and other analysts say.

Mr. Trump’s statements about Syria so far, Mr. Hof noted, came in a domestic political campaign in which he emphasized the threat of the Islamic State and played on fears of Muslims among his base, with no room for the nuances and contradictions of the Middle East. For instance, Mr. Trump has vowed to be tougher on Iran — which, along with Russia, provides decisive support to Mr. Assad.

Mr. Trump’s victory was closely watched across Syria. Like people the world over, Syrians reacted instantly with a mix of surprise, enthusiasm, despair and confusion.