Turkey is preparing to launch a new military operation in Syria, President Recep Tayyip Erdogan said on Wednesday, aimed at neutralizing US-backed Kurdish forces in the region.

“We will begin our operation to rescue the east of the Euphrates from the separatist organization within a few days,” Erdogan was quoted by The Associated Press as saying on state TV. “Our target is not the American soldiers, it is the terror organizations that are active in the region.”

Erdogan urged the US not to let “deep” disagreements on Syria policy prevent the two NATO allies from cooperating on other fronts.

The US warned that such a new offensive against the Kurds would be “unacceptable.”

“Unilateral military action into northeast Syria by any party, particularly as US personnel may be present or in the vicinity, is of grave concern. We would find any such actions unacceptable,” Commander Sean Robertson, a spokesman for the Department of Defense, told CNN.

“We believe this dialogue is the only way to secure the border area in a sustainable manner, and believe that uncoordinated military operations will undermine that shared interest,” he added.

The relationship between Turkey and the US has deteriorated steadily in recent years, helped in no small part by the strategic alliance between Washington and Kurdish forces throughout the region. Ankara views US-backed Kurdish military organizations, including the People’s Protection Units (YPG) based in Syria, as terrorist groups.

That point of contention flared up at the beginning of this year when Turkey launched Operation Olive Branch, a military incursion into Syria that successfully took territory from Kurdish opposition forces in the country’s northwest.