Washington dispatched a top envoy to meet with allied Kurdish forces inside Syria last week, a State Department official said Monday, following tensions after Turkey began operations in the war-torn country.

A State Department spokesman told AFP that Brett McGurk, the special presidential envoy to the U.S.-led coalition fighting DAESH, met with forces from the Kurdish-Arab Syrian Democratic Forces (SDF) alliance, which is led by the People's Protection Units (YPG).

The U.S. support to the YPG, and partnership in the fight against DAESH, has negatively affected its relations with Ankara, as Turkey, a NATO partner and a strategic ally of Washington, sees the group as a Syrian offshoot of the PKK terrorist group.

Ankara has reiterated numerous times that the YPG terror group consists a threat to Turkey's national security along its southern border due to its links with the PKK and that it will not allow establishing a YPG-controlled area to stop the spread of terrorism in the region.

The spokesman said McGurk pledged "ongoing U.S. support for the SDF in the fight against ISIL [DAESH], while emphasizing the need for strict adherence to prior commitments," a reference to demands the SDF withdraw to the east of the Euphrates. "In all of his meetings, he encouraged unity of effort and de-confliction between all the forces fighting ISIL [DAESH] in northern Syria," the spokesman said. McGurk also held talks last week in Turkey, the spokesman said. "He met with senior Turkish officials to discuss U.S. support for efforts to clear ISIL [DAESH] entirely from the border region... (and) also discussed planning for the Mosul campaign in Iraq, and closer U.S. and Turkish cooperation to accelerate ISIL's [DAESH] ultimate defeat."

Washington says that Turkey should focus its efforts in Syria on DAESH and refrain from engaging in confrontation with the YPG-led SDF. However, Ankara has continuously criticized the U.S.'s partnership with the YPG and urged the group to immediately return to the east bank of the Euphrates River, calling on the U.S. to fulfill its commitment in this regard.