The U.S. military is refusing to say whether it will move hundreds of its troops from a town in northern Syria after Turkey vowed to extend its anti-Kurdish offensive there, potentially bringing Turkish forces into confrontation with their American allies.

“They'll stay or they'll go. Don't know what the answer will be,” Lt. Gen. Kenneth “Frank” McKenzie, director joint staff for the U.S. military, told reporters at the Pentagon Thursday.

The status of the hundreds of U.S. troops in Manbij has been brought into question after Turkey vowed to extend its campaign against U.S.-backed Kurds from Afrin to Manbij, which lies further east.

A Turkish push towards Manbij would raise tensions between Ankara and Washington, already strained by Turkey’s cross-border campaign against the Syrian Kurds, who the U.S. has backed as a key ground ally in the battle against ISIS. While the U.S. has no troops in Afrin, the enclave targeted in the first phase of the Turkish offensive, it has hundreds of troops in Manbij, where they have been working with anti-ISIS forces for nearly a year, and a Turkish push there would carry a risk of U.S. forces getting caught in the crossfire.

Turkey’s Foreign Minister Mevlut Cavusoglu said Thursday that President Recep Tayyip Erdogan had asked President Donald Trump during a phone call Wednesday to remove U.S. forces from Manbij.

His statement came after a White House readout which gave a different account of the call, saying Trump had “urged Turkey to exercise caution and to avoid any actions that might risk conflict between Turkish and American forces.”

Turkish Deputy Prime Minister Bekir Bozdag reiterated demands Thursday that the U.S. should “stop supporting terrorists” if it wanted to avoid a potential confrontation with Turkey.

“The United States needs to review its solders and elements giving support to terrorists on the ground in a way to avoid a confrontation with Turkey,” he said.

McKenzie said U.S. troops in the region would coordinate closely with Turkish forces to let them know their positions and avoid unintended clashes, but that they would protect themselves.

“I would tell you that wherever U.S. troops are, they're going to be able to defend themselves, and we coordinate very closely with the Turks on that,” he said.

U.S. officials say there is no sign yet of Turkish forces moving toward Manbij.

The Turkish offensive against Kurdish forces in Afrin, which it considers to be linked to a banned Kurdish separatist group that has fought an insurgency against Ankara for decades, has claimed the lives of more than two dozen civilians, according to U.K.-based war monitor the Syrian Observatory for Human Rights.

The Turkish military said Friday it had killed 343 militants in northern Syria since the operation started.