Washington, October 7 (RHC)-- U.S. troops have begun withdrawing from northeast Syria ahead of a Turkish invasion that Kurdish fighters say will overturn the victory over the Islamic State of Iraq and the Levant (ISIL or ISIS) armed group.

Washington's forces "will not support or be involved in the [Turkish] operation" and "will no longer be in the immediate area," White House Press Secretary Stephanie Grisham said in a statement.  It was not clear whether that meant the United States would withdraw its 1,000 or so troops completely from northern Syria.  "Turkey will soon be moving forward with its long-planned operation into northern Syria," said the statement.

A U.S. official told Reuters news agency U.S. forces had on Monday evacuated two observation posts at Tel Abyad and Ras al Ain in northeast Syria, along the Turkish border.  Other U.S. troops in the region were still in position for now, the official said.

The withdrawal marks a major shift in U.S. policy and effectively abandons a U.S. ally in the battle against ISIL, which took over swathes of Syria before being defeated a year ago.  U.S. President Donald Trump on Monday defended the decision to withdraw American troops from northern Syria, saying it was too costly to keep supporting its allies.

"The Kurds fought with us but were paid massive amounts of money and equipment to do so. They have been fighting Turkey for decades," Trump said in a series of tweets. "Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds will now have to figure the situation out."
 
Turkish President Recep Tayyip Erdogan said on Monday his army was ready to launch operations against Kurdish fighters in Syria at any moment following the U.S. announcement.  "There is a phrase that we always say: we can come any night without warning," Erdogan told reporters in televised remarks. "It is absolutely out of the question for us to further tolerate the threats from these terrorist groups."

Syria's Kurds warned on Monday a Turkish military invasion would spark a major ISIL resurgence and vowed to battle Turkey's military.  Such an operation would reverse years of successful Kurdish-led operations to defeat the armed group and allow some of its surviving leaders to come out of hiding, the Syrian Democratic Forces (SDF) said in a statement.