U.S. President Trump said it was too costly to keep supporting Kurdish-led forces fighting IS Group, adding "it is time for us to get out of these ridiculous Endless Wars."
The United States began pulling troops back from the northeast Syria border Monday, opening the way for a Turkish strike on Kurdish-led forces long allied to Washington, in a move U.S. President Donald Trump hailed as a bid to quit "endless wars."
The major policy shift, which hands Turkey responsibility for thousands of jihadist prisoners, was denounced as a "stab in the back" by the Kurdish-led forces who have been Washington's partner in fighting the Islamic State group in Syria.
Trump said in several Tweets it was too costly to keep supporting Kurdish-led forces fighting IS Group, adding "it is time for us to get out of these ridiculous Endless Wars".
"Turkey, Europe, Syria, Iran, Iraq, Russia, and the Kurds will now have to figure the situation out," he said.
In a sign of deepening humanitarian concern, a U.N. official reacted to the move by saying civilians must be spared in any Turkish operation in the northeast, adding the United Nations hoped that displacement and atrocities can be prevented.
"We are hoping for the best but preparing for the worst," Panos Moumtzis, U.N. regional humanitarian coordinator for the Syria crisis, told reporters in Geneva.
A U.S. official said troops had withdrawn from two observation posts on the border, at Tel Abyad and Ras al-Ain, and had told the commander of the SDF that the United States would not defend the SDF from an imminent Turkish offensive. U.S. troops elsewhere in Syria remain in position.
The pullback will initially be limited in scope to a patch of territory near the Turkish border where both countries had been working to establish a special security area, a U.S. official told Reuters Monday.
The official, who spoke to Reuters on condition of anonymity, did not say whether the troops would leave the country or reposition elsewhere in Syria, where the United States has around 1,000 forces.
Another U.S. official said any unilateral Turkish military offensive in Syria was a "bad idea" and the United States "will not help it in any way, but will also not resist it".
In a statement after Trump spoke with Turkish President Tayyip Erdogan Sunday, the White House also stressed that U.S. troops would not support the operation. "United States forces, having defeated the ISIS territorial "Caliphate", will no longer be in the immediate area," it said.
A Turkish official later said the U.S. withdrawal could take one week, and Turkey would likely wait until it had been completed before launching an offensive.
The White House statement appeared to hand Turkey responsibility for Islamic State captives who are held in SDF facilities south of Turkey's initially proposed safe zone.
"Turkey will now be responsible for all ISIS fighters in the area captured over the past two years," it said. The statement made a pointed reference to Washington's European allies, saying many captured IS fighters came from those countries, which had resisted U.S. calls to take them back.
"The United States will not hold them for what could be many years and great cost to the United States taxpayer," it said.
In the first Turkish comment following the statement, Erdogan's spokesman Ibrahim Kalin said Turkey's "safe zone" plan was within the framework of Syria's territorial integrity.
"The safe zone has two aims: to secure our borders by clearing away terrorist elements and to achieve the return of refugees in a safe way," Kalin wrote on Twitter.
However, the Kremlin, the strongest foreign ally of Syrian President Bashar al-Assad, said Syria's territorial integrity had to be preserved and Moscow continued to seek the withdrawal of all foreign forces illegally present in Syria.
Turkey says it wants to settle up to 2 million Syrian refugees in the zone. It hosts 3.6 million Syrians sheltering from their country's more than eight-year-old conflict.