WASHINGTON—Turkey is asking the U.S. to provide substantial military support, including airstrikes, transport and logistics, to allow Turkish forces to assume the main responsibility for fighting Islamic State militants in Syria, senior U.S. officials say.
The Turkish requests are so extensive that, if fully met, the American military might be deepening its involvement in Syria instead of reducing it, the officials added. That would frustrate President Trump’s goal of transferring the mission of finishing off Islamic State to Turkey in the hope of forging an exit strategy for the U.S. military to leave Syria.
Discussions on how Turkey might take over the Syria mission will take place in the Turkish capital Ankara on Tuesday amid widespread skepticism at the Pentagon that Turkey can adequately replicate the U.S. mission.
Participants will include White House national security adviser John Bolton; Gen. Joe Dunford, the chairman of the Joint Chiefs; and James Jeffrey, the State Department envoy for Syria.
One U.S. official said the administration is unlikely to provide all of the military support the Turks are seeking, especially on air support.
Mr. Trump said last month he had reached a deal with Turkish President Recep Tayyip Erdogan for Turkey’s military to replace the more than 2,000 U.S. troops in Syria.
The Trump administration’s initial plan was to withdraw the forces within 30 days. The president later slowed the timetable after widespread criticism about the risks to the abruptly announced plan.
On Friday, U.S. officials again recalibrated administration plans and suggested that the withdrawal could drag out for months.
“We have no timeline for our military forces to withdraw from Syria,” said one senior State Department official.
Before firming up withdrawal plans, U.S. officials are seeking assurances from Turkey that its forces won’t “slaughter the Kurds” when they enter Syria, Secretary of State Mike Pompeo said earlier this week. U.S. officials also want to prevent a security vacuum from opening that allows Islamic State fighters to regroup.
While there may be no firm timeline, a senior administration official traveling to the Middle East with Mr. Bolton said the president had received assurances that the U.S. military withdrawal “can be done in weeks.”
For now, the basic U.S. strategy to hand over the fight to Turkey remains unchanged. It was codified in a classified memo Mr. Bolton recently sent to cabinet-level officials, U.S. officials said.
Mr. Bolton also wrote in the memo that the administration’s prior policy objectives in Syria are unchanged. Those goals have included defeating Islamic State, evicting Iranian-commanded forces, and pursuing a diplomatic end to the civil war.
Proponents of Mr. Trump’s strategy assert the administration’s basic plan is intact. But skeptics within the government cite a wide gap between the White House’s goals and the ability to carry it out.
Mr. Trump embraced Mr. Erdogan’s offer to take on the mission against Islamic State in a Dec. 14 phone call in a decision that surprised both former Defense Secretary Jim Mattis and Brett McGurk, the U.S. envoy to the coalition fighting Islamic State, said people familiar with their thinking. Both subsequently resigned.
Turkey’s request for air cover, the sharing of intelligence and other military support was conveyed to Gen. Dunford in late December with his Turkish counterpart.
Three U.S. military officials cited a widespread view that the Turks couldn’t replicate the role that the American military has played in Syria against Islamic State, noting an array of logistical and political challenges facing Turkey. A number of intelligence analysts share that view, a U.S. official said.
“I haven’t heard anyone say they think the Turks can do it,” one of the military officials said.
President Trump ordered the withdraw of U.S. troops from Syria, and declared that America had “defeated ISIS.” WSJ’s Gerald F. Seib discusses the significance of the decision and its consequences. Photo: AP
Specifically, the officials said they don’t believe the Turkish military has the logistical capacity to move their forces deep into Syria’s Middle Euphrates River Valley to battle the several thousand remaining Islamic State militants and provide the supplies they would need.
The officials also questioned Turkey’s ability to carry out a substantial air campaign involving round-the-clock missions with reconnaissance aircraft and attack planes equipped with precision munitions against the terror group. Air power has been a key part of the U.S.-led coalition campaign.
While Turkey has supported some local forces, Syrian groups that Turkey has backed aren’t deemed by U.S. officials to be effective fighters.
Many experts and officials also fear the Turks may target Kurdish fighters who have long provided the U.S. with solid support in the campaign against Islamic State militants and endured considerable loss of life.
To try to mitigate these risks, Mr. Jeffrey, the State Department envoy, is seeking to forge an arrangement with the Turks that would allow them to enter northern Syria while avoiding largely Kurdish areas, say U.S. officials familiar with the plans.
Mr. Jeffrey and his State Department team have created a color-coded map of northeastern Syria in an attempt to negotiate a power-sharing plan that could avert a costly Turkish-Kurdish fight in the area.
However, keeping their forces apart should Mr. Erdogan’s troops enter Syria could prove difficult. One former U.S. official described the map as “Sykes-Picot on acid,” a reference to the secret post-World War I deal between France and England that carved the Middle East into colonial spheres of influence.
If U.S. forces eventually leave, one key question for the Trump administration to address is what to do with the Syrian Democratic Forces, the 60,000-strong, Kurdish-led force backed by the U.S. military in the fight against Islamic State.
Mr. Jeffrey has asked Gen. Mazloum Abdi, the Kurdish commander of Syrian fighters, to hold off on making any deals with President Bashar al-Assad’s government while the Trump administration tries to develop its strategy.
Forging an alliance with the Assad regime would be one way for the Kurdish fighters to protect themselves against a potential attack by the Turkish military and to retain some degree of control over northeastern Syria.
Mr. Jeffrey is taking over Mr. McGurk’s responsibilities as the top U.S. representative to the coalition fighting Islamic State, while retaining his duties as the senior envoy on Syria policy, the State Department said Friday.
Emre Ozkan, a counselor at the Turkish Embassy in Washington, said he had no information to offer on military planning by his government and the U.S.
Despite Mr. Trump’s assertion on Dec. 19 that the U.S.-led coalition had defeated Islamic State, strikes against the terror group have since increased. From Dec. 16-29, there were 469 coalition strikes against the group in Syria, according to the coalition. Among the targets were command and control nodes, explosive facilities, weapons caches and one “unarmed aircraft system,” the U.S. military said in a statement. Between Dec. 9-15, the coalition said it conducted 208 strikes in Syria.
The U.S. also is considering moving ships toward the region in case troops come under attack while leaving the country, a military official said. Withdrawing from a war zone is a particularly vulnerable time for troops as they move large amounts of people and equipment out of the country. An amphibious assault ship, for example, carries helicopters, aircraft and hundreds of troops and could mitigate that risk, a defense official said.
Mr. Erdogan previously offered to take on the fight against Islamic State during the Obama administration, but U.S. officials believed then that Turkey was promising more than it could deliver and noted that the Turks were assuming they would have support from the U.S. military.
“Pentagon officials were very skeptical of the Turks ability to deliver on the ground in the fight against” Islamic State, a former Obama administration official said.
—Vivian Salama in Washington contributed to this article.