U.S.-allied Syrian Kurds have expressed deep reservations about Washington’s sudden decision to withdraw American troops from Syria, saying such a move amounts to a “betrayal” that leaves them vulnerable to attacks by Turkey and warning that it would lead to a resurgence of the Islamic State (ISIS/ISIL).

In a statement carried by various news outlets, the Kurdish People’s Protection Units (YPG)-led Arab-Kurdish alliance known as the Syrian Democratic Forces (SDF) declared, “The war against Islamic State has not ended, and Islamic State has not been defeated.”

Any withdrawal would “create a political and military vacuum in the area, leaving its people between the claws of hostile parties,” it added.

Acknowledging that the Kurds are concerned, Sky News quoted the SDF as warning that a U.S. withdrawal will lead to a “revival” of ISIS.

“We have every right to be afraid,” Arin Sheikmos, a Kurdish journalist and commentator, told the Associated Press (AP). “If the Americans pull out and leave us to the Turks or the [Syrian] regime, our destiny will be like the Kurds of Iraqi Kurdistan in 1991. Neither the regime, nor Iran nor Turkey, will accept our presence here.”

“Everyone is upset, sad and afraid,” an anonymous SDF member told Fox News, referring to the U.S. withdrawal announcement. “It’s a historic mistake. We wanted to be part of America. We are surrounded by enemies, and ISIS isn’t even finished yet.”

“We are being told that the Pentagon is pushing back — which is why we are being careful in what we are saying now,” an unnamed YPG commander told Voice of America (VOA), adding, “But if there isn’t change of heart, this will be green-light for Turkey to attack.”

Citing fears of retaliation, most Syrian Kurds spoke to media outlets on condition of anonymity.

The U.S. decision to withdraw from Syria came as Turkey was preparing to deploy its military into Syria to confront Kurdish militias that it accuses of threatening its sovereignty.

The U.S. warned Turkey against the move, but now that American forces are slated to leave, some Kurds are accusing the United States of abandoning them.

According to Bas News and the Guardian, the SDF described the U.S. withdrawal as a “blatant betrayal” and accusing America of stabbing them in the back.

Ankara has long considered Syrian Kurdish groups to be an extension of the Kurdistan Worker’s Party (PKK) terrorist group that is waging an insurgency inside Syria.

U.S. support for the Syrian Kurds has infuriated Ankara, which has repeatedly demanded that America stop backing the YPG.

Echoing other assessments, the SDF believes a U.S. withdrawal is a boon for Iran, Turkey, and the regime of the Tehran and Moscow-backed dictator Bashar al-Assad in Syria.

“Even U.S. officials working with us inside Syria were surprised by this. Unfortunately, this will empower Iran and increase its influence in Syria and beyond. And thus it will also weaken pro-American actors in Syria and in the region, including Turkey,” an unnamed SDF official told VOA.

“If the Americans are leaving, then al-Assad forces are likely to take full control of our region,” Ibrahim Biro, an official with the Kurdish National Council, an opposition group in Syria, added.

The Kurdish Democratic Union Party (PYD), the political wing of the YPG, has managed to maintain control of large swathes of territory in northeastern Syria, courtesy of the weapons, air support, and around 2,000 special forces troops on the ground provided by the United States.

Citing Syrian Kurdish commanders, VOA noted that the Trump administration has vowed to continue to the fight against ISIS. Moreover, the Pentagon is reportedly expected to keep the estimated 5,200 troops already deployed in neighboring Iraq. Those troops will reportedly have the ability to launch attacks into Syria, if necessary.

“Syrian Kurdish commanders say they had been given assurances by their American partners of a continued U.S. military presence — at least until IS couldn’t mount any kind of resurgence and there is greater stability in northern Syria,” VOA reported.

U.S. military officials consider the SDF, a Kurdish-Arab alliance, to be the most effective troops against ISIS on the ground. The YPG leads and makes up the majority of the SDF.

On Wednesday, U.S. President Donald Trump’s administration announced that it had begun to pull its nearly 2,000 troops from Syria.

“We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency,” President Trump declared on Twitter. However, U.S. government and independent assessments have recently warned that the mission against the group is not over, noting that ISIS remains a threat to Iraq and Syria.

Radwan Badini, a professor of journalism at Salahaddin University in Erbil, Iraqi Kurdistan, told VOA that a U.S. withdrawal could trigger retaliation against those who helped the United States.

Northeastern Syria is “an ethnically diverse region with many people still sympathizing with [ISIS]. So the U.S. move to pull out from Syria could inspire some people to retaliate against others who cooperated with the Americans in the fight against [ISIS],” he told VOA.

On Monday, Turkish President Recep Tayyip Erdogan “claimed he had won concessions from Washington during a lengthy phone conversation with Trump about a new offensive against the U.S.-allied YPG,” VOA noted.

For months, American troops have served as a buffer between Turkey and the Kurds in Syria, helping to reduce tensions between the two sides.

Russia, Turkey, Iran, and the Assad regime have welcomed the prospective U.S. military withdrawal from Syria.