The White House has given the green light for a long-threatened Turkish assault on Kurdish-held Syria, effectively abandoning its allies who fought and defeated Islamic State.
The US had for months been working with Turkey to try to create a buffer zone along its border with northern Syria between the Turkish military and Kurdish forces which Ankara sees as terrorists.
Turkey has repeatedly criticised its slow implementation and threatened a unilateral assault, but until now the US had refused to stand aside.
US Republican and Democrats had warned such an offensive on the Kurdish People’s Protection Units (YPG), which lost 11,000 troops in the battle against Isil, could lead to a massacre of Kurds and send a worrying message to American allies across the world.
“Turkey will soon be moving forward with its long-planned operation into northern Syria,” the White House said in a statement.
“The United States Armed Forces will not support or be involved in the operation, and United States forces, having defeated the ISIS territorial “Caliphate,” will no longer be in the immediate area.”
The US began pulling back some of its 1,000 troops from border towns Tel Abyad and Ras al-Ayn on Monday, and has said it will potentially depart the country should widespread fighting break out.
The announcement appeared to take both the Kurds and US coalition forces, which had been carrying out joint patrols with Turkey on the ground, completely by surprise.
Kurdish sources say they were acting in good faith trying to establish a security mechanism with the US to placate Turkey, but now felt that Ankara had been using it as a cover for reconnaisance.
Mustafa Bali, spokesman for the Kurdish-led Syrian Democratic Forces (SDF), tweeted: “We are not expecting the US to protect NE #Syria. But people here are owed an explanation regarding security mechanism deal, destruction of fortifications and failure of US to fulfill their commitments.”
The White House statement was released after a phonecall between US President Donald Trump and Turkish President Recep Tayyip Erdogan on Sunday night.
Mr Erdogan had reportedly assured the US president that Ankara would take over the detention of Isil militants captured by the SDF, on the battlefield.
The Kurds have been holding thousands of Syrian and thousands more foreign Isil suspects in prisons and camps across the north of the country.
Mr Trump has repeatedly asked countries under the US-led coalition against Isil to repatriate their citizens. However, the UK, France, Germany, and other allies have so far refused.
“The United States will not hold them for what could be many years and great cost to the United States taxpayer,” the White House statement said. “Turkey will now be responsible for all ISIS fighters in the area captured over the past two years in the wake of the defeat of the territorial “Caliphate” by the United States.”
The decision is a massive blow to the Kurds, who not only helped hold back Isil but have for years been building an autonomous statelet in the northeast of Syria.
Turkey claims its planned “safe zone” is to purge the border of YPG forces, which it sees as a terrorist offshoot of the Kurdistan Workers’ Party (PKK), which has fought an insurgency inside its territory for the past 35 years.
The proposed corridor would have an initial depth of 18 miles and a length of 300 miles and includes the Kurds’ biggest urban centres, including the city of Qamishli which has an estimated 250,000 population.
Western diplomats told the Telegraph they are working on the theory that Mr Erdogan will begin by attempting to take a smaller sliver between the towns of Tel Abyad and Ras al-Ain on the border, but the president himself has hinted at much wider ambitions.
Mr Erdogan has said he wants to return two million of mostly Sunni Muslim Arab Syrian refugees he is hosting in Turkey to the buffer zone, which some have said would amount to an ethnic repopulation.
The Kurds fear many of the Syrians that might be placed in the zone are not native to north-east Syria, and might displace the Kurdish culture and rights.
The UN said that it was “preparing for the worst”, fearing an assault would send large numbers of civilians fleeing.
“This Turkish military operation in northern and eastern Syria will have a significant negative impact on our war on ISIS and will destroy everything that has been achieved from the state of stability over the past years,” the Kurdish-led Syrian Democratic Forces said in a statement.
They said they would defend themselves against “Turkish aggression” and called on all sects, including Kurds, Arabs, Syriacs and Assyrians to join them.
Defending its Kurdish allies would have seen the US come against its Nato partner Turkey, which Washington was keen to avoid.
President Donald Trump has since taking office attempted to disentangle the US from drawn-out wars in the Middle East.
His goal of swift withdrawals in Syria, Iraq and Afghanistan have been stymied by concerns from US officials and American allies about the dangerous voids that would remain.