France will maintain its participation in the coalition fighting the militant Islamic State (IS) group in Syria, a government minister said on Thursday after US President Donald Trump surprised Washington's allies by ordering US troops home.

“For now of course we remain in Syria,” France's European Affairs Minister Nathalie Loiseau said on CNews television, adding "the fight against terrorism is not over."

“It's true that the coalition has made significant progress in Syria, but this fight continues, and we will continue it,” she said.

France has stationed fighter jets in Jordan and artillery along the Syrian border in Iraq as part of the US-led coalition, as well as an undisclosed number of special forces on the ground.

Its allies have warned that despite losing most of the territory it once controlled during the bloody Syrian civil war, the IS threat has not been totally eradicated.

French Defence Minister Florence Parly took to Twitter on Thursday to say that the IS group “has not been wiped of the map, nor have its roots.” “We must definitively defeat the last pockets of this terrorist organisation,” she added.

Earlier on Wednesday, US President Donald Trump declared that the IS group had been “beaten” in Syria and announced a stunning order to pull American ground forces from the war-ravaged nation.

The momentous decision to withdraw, which runs counter to long-established US policy for Syria and the region, blindsided lawmakers, the Pentagon and international allies alike.

“We've won against ISIS,” Trump said in a short video posted on Twitter. “We've beaten them and we've beaten them badly. We've taken back the land. And now it's time for our troops to come back home.”

A withdrawal could have extraordinary geopolitical ramifications, and plunges into uncertainty the fate of US-backed Kurdish fighters who have been tackling IS militants, thousands of whom are thought to remain in Syria.

A US official had told AFP that Trump's decision was finalised on Tuesday. “Full withdrawal, all means all,” the official had said when asked if the troops would be pulled from across Syria.

Currently, about 2,000 US forces are in the country, most of them on a train-and-advise mission to support local forces fighting the IS group. A Pentagon spokeswoman has said the Defense Department had “started the process” of bringing troops home.