The United States will withdraw all of its troops from Syria, a US official has said, after President Donald Trump claimed America has "defeated ISIS" in the war-ravaged country.
The move will have extraordinary geopolitical ramifications - and plunges into uncertainty the fate of US-backed Kurdish fighters who have been tackling so-called Islamic State jihadists, hundreds of whom remain in Syria.
"We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency," the Republican leader tweeted.
The US official told AFP that Mr Trump's decision was finalised yesterday.
"Full withdrawal, all means all," the official said when asked if the troops would be pulled from across all of Syria.
Currently, about 2,000 US forces are in Syria, most of them on a train-and-advise mission to support local forces fighting IS.
Critics from both main political parties were quick to assail Mr Trump's decision, saying it could embolden Ankara to attack US-backed Kurdish fighters.
Republican Senator Marco Rubio called the move a "terrible mistake," while Democratic Senator Jack Reed said it amounted to a "betrayal" of the Kurds that "provides further evidence of President Trump's inability to lead on the world stage."
Most US troops are stationed in northern Syria, though a small contingent is based at a garrison in Al-Tanaf, near the Jordanian and Iraqi borders.
Mr Trump had previously voiced skepticism about the US presence in Syria, saying in March he wanted to bring troops home "soon."
But the president's military advisors and international allies warned him against a precipitous pullout and the mission continued.
The US official would not provide a timeline, saying only: "We will ensure force protection is adequately maintained, but as quickly as possible."
Echoing Mr Trump, White House spokeswoman Sarah Sanders said IS has been defeated territorially, but the US-led coalition that includes dozens of nations would continue fighting the jihadists.
"These victories over ISIS in Syria do not signal the end of the Global Coalition or its campaign," Ms Sanders said in a statement.
A Pentagon spokeswoman said the department had "started the process" of bringing troops home.
It was not immediately known what effect the troop withdrawal would have on air operations in Syria. These have been ongoing since late 2014.