WASHINGTON — As Trump administration officials try to convince allies that the United States remains committed to the fight against the Islamic State in Syria they are facing a significant roadblock: President Trump’s own policy reversals.
At a high-level State Department meeting scheduled for Thursday, diplomats from 35 nations and international organizations will be asked to stick with the campaign to eradicate the extremist group even after its leader, Abu Bakr al-Baghdadi, was killed in an American raid last month.
But confusion over the Trump administration’s policy in northeast Syria has discouraged allies, according to several diplomats, who said it has fomented doubt that whatever agreements are struck could be reversed by the president.
Mr. Trump said on Wednesday that hundreds of American troops remain in northeast Syria, but only to secure oil-rich territory there.
“We’re keeping the oil,” Mr. Trump said at the White House ahead of a meeting with President Recep Tayyip Erdogan of Turkey. “We have the oil. The oil is secure. We left troops behind only for the oil.”
A day earlier, a senior State Department official said the primary role of the relatively small deployment of American military personnel in northeast Syria was to counter the Islamic State. Securing the oil fields was a “secondary mission,” said James F. Jeffrey, the diplomat who oversees Syria issues and is the top liaison to the American-led global campaign against the extremist group.
“U.S. forces in northeast Syria are there under an authorization to fight terrorism, specifically to ensure the enduring defeat of ISIS,” Mr. Jeffrey said, using an acronym for the Islamic State. “That is our overall mission.”
It was just one example of the policy whiplash that foreign diplomats described since an Oct. 6 telephone call between Mr. Trump and Mr. Erdogan.
Following that call, Mr. Trump ordered American troops out of Syria, surprising his aides and foreign allies. Days later, Mr. Erdogan launched an invasion of Syrian territory that had been held by Kurdish fighters who Turkey views as terrorists — but who had allied with American forces against the Islamic State.
Mr. Trump has since reversed his withdrawal order to keep under 1,000 American troops in Syria. But given the uncertainty of their mission — and how long they will remain — allies are hedging their support for the continued fight.
European efforts to provide humanitarian aid, resettle refugees and clear explosives have largely been put on hold until the United States can assure that the area is safe. In a statement on Wednesday, the French foreign ministry noted that Syrian territory was wrested from the Islamic State only seven months ago, and urged against “any unilateral initiative that could undermine this achievement.”
One foreign diplomat said Thursday’s meeting would focus on what he described as a loss of clear strategy by the United States in Syria. Another predicted the high-level talks would amount to little more than a meet-and-greet. Both spoke on condition of anonymity to discuss the sensitive diplomacy.
“It’s quite clear that the president has been convinced to retain troops on the only basis that might have been of interest to him — the existence of oil,” said Charles R. Lister, a senior fellow at the Middle East Institute. “But the much bigger U.S. government apparatus is trying to use that as a cover to form a more meaningful, less ambiguous and more sustainable strategy focused on countering terrorism while reasserting leverage over Damascus.”
How to deal with an estimated 10,000 Islamic State fighters who are detained in Kurdish-controlled camps in northeast Syria will be among the top topics at Thursday’s talks.
The vast majority of the fighters — about 8,000 — are Syrian and Iraqi. They are too dangerous to release, yet too vulnerable to abuse by security forces if they were to be transferred to the custody of their respective governments for trial, officials said.
A State Department official said the rest of the Islamic State fighters are largely in limbo, given that most European nations have refused to take back their citizens for prosecution.
The United States has repatriated at least six Islamic State fighters, said the official, who spoke on condition of anonymity.
In all, 13 Americans who joined the Islamic State abroad have returned to the United States, but not all were fighters and some came back on their own, said Seamus Hughes, the deputy director of the George Washington University Program on Extremism.
American officials are closely watching Turkish forces to make sure they do not approach areas where the Islamic State detainees are being held, fearing attacks on Kurdish guards stationed there.
There are also 70,000 wives and children of ISIS fighters in camps, and Western nations are struggling with both whether they should take back their citizens and how to do so, given that some have become radicalized or are otherwise violent.
Mr. Erdogan’s government this week began the process of deporting Islamic State fighters held in Turkish detention centers to France, Germany, Denmark and Ireland. It also deported to the Greek-Turkish border a man believed to be an American citizen accused of joining the Islamic State.
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.