Turkish President Recep Tayyip Erdogan vowed on Friday to purge his country’s border from “terrorists”, saying that Ankara may expand its current operation in northwestern Syria to the Iraqi border. “Operation Olive Branch will continue until it reaches its goals. We will rid Manbij of terrorists, as it was promised to us, and our battles will continue until no terrorist is left until our border with Iraq,” Erdogan said in a speech in Ankara. Any drive by Turkish forces toward Manbij, part of Kurdish-held territory some 100 km (60 miles) east of Afrin, could threaten U.S. efforts in northern Syria. The United States has about 2,000 troops in Syria, officially as part of the international, US-led coalition against the ISIS terrorist group. Many are deployed in Manbij and an expansion of Turkish operations there has sparked fears of a clash between the two NATO allies. Washington has angered Ankara by providing arms, training and air support to the Syrian Kurdish forces. Turkey sees the People’s Protection Units (YPG) as an extension of the outlawed Kurdistan Workers Party (PKK), which has waged a deadly insurgency in Turkey’s largely Kurdish southeast for three decades. “How can a strategic partner do this to its partner?” Erdogan said, referring to the United States. “If we will wage a battle against terror together, we will either do this together or we will take care of ourselves.”