President Trump ordered military leaders this week to plan for a rapid withdrawal from Syria, declaring victory over the Islamic State. (Us Army/Reuters)

The Trump administration has not yet decided whether it will continue airstrikes in Syria after American troops depart, a defense official said Thursday, one of several questions officials have scrambled to answer in the wake of the president’s abrupt withdrawal announcement.

The fate of the four-year air campaign will be an important indicator for whether the United States will employ its military power in Syria after the exit of the more than 2,000 U.S. troops now positioned there.

President Trump, acting on a long-standing desire to end the military presence in Syria, ordered military leaders this week to plan for a rapid withdrawal, declaring victory over the Islamic State.

While the president had repeatedly threatened to end the mission in Syria, his announcement surprised military officials, who had been planning for an ongoing mission to ensure the Islamic State does not regroup.

Militants have lost control of vast areas across Iraq and Syria but remain arrayed in small cells in eastern Syria and control several hundred square miles of territory.

The official, speaking on the condition of anonymity to discuss internal deliberations, said the U.S. military would use air power until U.S. troops withdraw but that officials were still considering whether they would continue beyond that.

The timeline for the departure is another issue the U.S. Central Command, which oversees forces in the Middle East, and the Pentagon’s Joint Staff were working to clarify.

One function of U.S. forces in Syria, who work with numerous local forces, has been to help guide the air campaign.

“That’s a very, very well-oiled process, so that’s highly desirable,” said David Deptula, a retired Air Force lieutenant general who now heads the Mitchell Institute for Aerospace Studies. “But frankly we can continue with small elements of covert forces,” or work exclusively through local troops in the absence of any American personnel.

The U.S. military also has extensive intelligence capabilities including drones, surveillance aircraft, satellite imagery and other electronic tools that could provide information needed to develop targets on the ground.

U.S. aircraft conducted strikes for about a year before President Barack Obama authorized the first military troops to enter Syria in the fall of 2015. Today, U.S. and allied aircraft fly over much of northern and eastern Syria, using a phone channel to deconflict with Russian and Syrian planes.

The military could conduct periodic strikes against senior members of the Islamic State. It would also be likely to use its aircraft to protect other members of the U.S.-led military coalition who remain on the ground. France has said it will keep some forces in Syria for the time being.

American air power is unlikely to be used to protect the Kurdish-led Syrian Democratic Forces, the chief local partner of the United States in Syria, unless it is battling the Islamic State.

Turkey, which considers the SDF part of a Kurdish terrorist group, said Thursday that it would “bury” Kurdish forces in Syria and that it was preparing to launch a military offensive against the SDF in the coming days.