Asharq Al-Awsat

US Defense Secretary Mark Esper warned Turkey on Tuesday that Washington would prevent unilateral incursions into northern Syria against Kurdish forces.

On Sunday, President Recep Tayyip Erdogan said Turkey, which already has a foothold in northwest Syria, will carry out a military operation in a Kurdish-controlled area east of the Euphrates in northern Syria.

“Clearly we believe any unilateral action by them (Turkey) would be unacceptable,” Esper told reporters traveling with him to Japan.

“What we’re going to do is prevent unilateral incursions that would upset, again, these mutual interests... the United States, Turkey and the SDF share with regard to northern Syria,” Esper said.

The SDF stands for the Syrian Democratic Forces. With US backing, the SDF, which includes the Kurdish People’s Protection Units (YPG), have taken control over the last four years of much of northeastern Syria from ISIS. Ankara sees the YPG as a terrorist organization.

Esper said the United States did not have any “ambition” to abandon the SDF, but stopped short of guaranteeing that the United States would protect them in case of a Turkish operation.

He said the US is trying to work out an arrangement that addresses Turkey's concerns, adding: "I'm hopeful we'll get there."

He did not provide details on where progress is being made.

A team from the Pentagon was in Turkey to speak with Turkish officials about the issue.

Esper suggested that a Turkish operation into northern Syria could affect the SDF’s focus on ensuring ISIS did not retake the territory it once held in Syria and the ability of the US-backed forces to hold the thousands of alleged ISIS fighters in detention.

Esper said the US will not abandon its SDF allies.

The Turkish-led campaign, which has for months been delayed due to resistance from Washington, is aimed at evicting YPG forces from a string of border town in Raqqa and Hasaka provinces.

Ankara has accused Washington of stalling progress on setting up a safe zone inside Syria’s northeastern border with Turkey that would be cleared of the YPG.

This week, Erdogan said both Russia and the United States had been told of the planned operation, but did not say when it would begin. It would mark the third Turkish incursion into Syria in as many years.

Hundreds of US troops are stationed east of the Euphrates River in northern Syria working with the SDF, and an incursion by Turkey could put them in the middle of any firefight between Turkish and Kurdish forces.

Turkey and the US have been negotiating for months over the establishment of a safe zone along the Syrian border that would extend east of the Euphrates to Iraq.

Turkey wants to establish a 25-mile-deep zone. But so far the two sides have failed to reach an agreement.

Ties between the two NATO allies have been strained over a host of issues, including the United States’ removal of Turkey from the F-35 fighter jet program after Ankara bought and took delivery of Russian S-400 missile defenses that Washington sees as a threat.