Trump shocked the US establishment and international allies Wednesday when he announced that all US troops would be withdrawn from Syria.

He did not address the air campaign, in which the United States and partner nations including France and Britain have spent years pounding IS targets across the country.

Pentagon spokeswoman Commander Rebecca Rebarich said the US would continue its air war while American soldiers were in Syria -- but she would not say if the campaign would continue afterward.

"As long are there are troops on the ground, the US will conduct air strikes in support of our forces," Rebarich told AFP.

"As for anything post-US troops on the ground, we will not speculate on future operations."

A US defense official told AFP that "there's not a lot of clarity on the future situation."

"What we do in the air campaign will depend on the situation on the ground, and what partners and allies who are continuing the fight against ISIS do," the official said.

France and Britain have already indicated they will continue counter-IS operations.

The air war has been the keystone of US operations in Syria, with warplanes and drones hammering IS targets since 2014.

According to the most recent official strike summary, published on Wednesday, the US-led coalition conducted 208 air and artillery strikes in Syria last week.