Turkey will soon invade northern Syria while the United States is to remove all of its forces from the area, the White House has said.
The move casts uncertainty on the fate of the Kurdish fighters who have been allied with the US in a campaign against Islamic State but are viewed as terrorists by Turkey.
White House press secretary Stephanie Grisham said US troops "will not support or be involved in the operation" and "will no longer be in the immediate area".
Turkey will take custody of foreign fighters captured in the US-led campaign against the Islamic State group who have been held by the Kurdish forces, she added.
Kurdish forces bore the brunt of the ground campaign against Islamic State militants.
In December, US president Trump announced he was withdrawing American troops from Syria but was met with widespread condemnation for abandoning Kurdish allies to the Turkish assault.
The announcement prompted the resignation in protest of then-Defence Secretary Jim Mattis, and a coordinated campaign by then-national security adviser John Bolton to try to protect the Kurds.
Additional reporting by the Associated Press
