U.S. training of Syrian Kurdish and Arab forces could risk an agreement between Turkey and the United States to establish a law enforcement force in northeast Syria as a part of a deal to set up a safe zone, columnist Hande Fırat wrote in the Hürriyet newspaper on Friday.

The deal for the establishment of the safe zone agreed last month was expected to ease tensions that have escalated over Turkey’s national security concerns related to Kurdish-held territories in northeast Syria.

Fırat said Ankara and Washington had agreed that people related to terrorism would be removed from the police force that would be established by the two countries in the safe zone.

“Despite the deal, there are allegations that the United States has started to establish these militia forces unilaterally. According to the information I obtained from local forces, the United States has started training a Kurdish-Arab force it has established unilaterally,” Fırat said. “This is not something Ankara can accept. And it is against the agreement.”

Turkey sees the Syrian Democratic Forces (SDF), and its Kurdish affiliate, the People’s Protection Units (YPG) as an offshoot of the outlawed Kurdistan Workers’ Party (PKK), while the SDF is the main partner of the U.S.-led coalition forces fighting Islamic State in Syria.

Meanwhile, the official Twitter account of the Special Operation Joint Task Force fighting against ISIS on Thursday shared footage showing SDF training on Aug. 3.

“@CJTFOIR forces trained the cadets in Military Operations in Urban Terrain as part of a summer training cycle,” it said.