At the White House on Wednesday, Mr. Trump praised Mr. Erdogan for what he described as the capture of more than 100 Islamic State fighters. He said Europe’s reluctance to take back its citizens “is not right, and is not fair.”
Diplomats said France and Qatar are working on proposals for an international tribunal to prosecute Islamic State fighters instead of leaving it to individual governments.
Since Mr. al-Baghdadi’s death, senior State Department and Pentagon officials, as well as top American generals, have sought to explain the continued American troop presence in northern Syria more as a priority to defeat ISIS, working with Syrian Kurdish allies, than to protect oil fields.
On Sunday, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, also emphasized a counterterrorism mission for the 600 to 700 troops that likely will remain in northern Syria.
“There are still ISIS fighters in the region and unless pressure is maintained, unless attention is maintained on that group, then there’s a very real possibility that conditions could be set for a re-emergence of ISIS,” General Milley said on ABC’s “This Week.” “The footprint will be small, but the objective will remain the same, the enduring defeat of ISIS.”
But security experts with experience in the region warn that the evolving, even ad hoc troop arrangement the United States has adopted in northeast Syria will likely only forestall another major conflict between the Syrian Kurds and the Turkish army and its proxies in the country.
“You can’t have a local Syrian partner as the only force to fight ISIS, and at the same time you won’t protect them from being attacked on their flank by a country you’re calling your ally,” said Nicholas A. Heras, a fellow at the Center for a New American Security who has advised Kurdish forces in Syria.
Rukmini Callimachi contributed reporting from New York.