Washington has had troops in Syria for years as part of international efforts against the Islamic State (IS) group, which rose out of the chaos of the country's civil war to seize swaths of territory there and in neighboring Iraq over a decade ago.

The brutal jihadists have since suffered major defeats in both countries, but still remain a threat.

"Today the secretary of defense directed the consolidation of US forces in Syria... to select locations," Pentagon spokesman Sean Parnell said in a statement, without specifying the sites where this would take place.

"This deliberate and conditions-based process will bring the US footprint in Syria down to less than 1,000 US forces in the coming months," he said.

"As this consolidation takes place... US Central Command will remain poised to continue strikes against the remnants of (IS) in Syria," Parnell added, referring to the military command responsible for the region.

President Donald Trump has long been skeptical of Washington's presence in Syria, ordering the withdrawal of troops during his first term but ultimately leaving American forces in the country.

As Islamist-led rebels pressed forward with a lightning offensive last December that ultimately overthrew Syrian president Bashar al-Assad, Trump said Washington should "NOT GET INVOLVED!"

"Syria is a mess, but is not our friend, & THE UNITED STATES SHOULD HAVE NOTHING TO DO WITH IT. THIS IS NOT OUR FIGHT," Trump, then the president-elect, wrote on his Truth Social platform.

- Years of war against IS -

The 2014 onslaught by IS prompted a US-led air campaign in support of local ground forces -- the Kurdish-led Syrian Democratic Forces (SDF) and Iraqi government units.

Washington also deployed thousands of American personnel to advise and assist local forces, with US troops in some cases directly fighting the jihadists.

After years of bloody warfare, Iraq's prime minister announced a final victory over IS in December 2017, while the SDF proclaimed the defeat of the group's "caliphate" in March 2019 after seizing its final bastion in Syria.

But the jihadists still have some fighters in the countryside of both countries, and US forces have long carried out periodic strikes and raids to help prevent the group's resurgence.

Washington stepped up military action against IS in Syria in the wake of Assad's overthrow, though it has more recently shifted its focus to strikes targeting Yemen's Huthi rebels, who have been attacking international shipping since late 2023.

US forces in Iraq and Syria were repeatedly targeted by pro-Iran militants following the outbreak of the Gaza war in October 2023, but responded with heavy strikes on Tehran-linked targets, and the attacks largely subsided.

Washington for years said it had some 900 military personnel in Syria as part of international efforts against IS, but the Pentagon announced in December 2024 that the number of US troops in the country had doubled to around 2,000 earlier in the year.

While the United States is reducing its forces in Syria, Iraq has also sought an end to the US-led coalition's presence there, where Washington has said it has some 2,500 troops.

The United States and Iraq have announced that the coalition would end its decade-long military mission in federal Iraq by the end of 2025, and by September 2026 in the autonomous Kurdistan region.