Turkish presidential spokesman Ibrahim Kalin on Sunday held talks with US National Security Adviser H. R. McMaster focused on cooperation between the two countries in the fight against terrorism. The two also tackled controversial files, especially US support to Kurdish militias in northern Syria. Ankara has long demanded the US severs ties with the Kurdish Peoples Protection Units. The meeting took place on the eve of US Secretary of State Rex Tillersons visit to Ankara. His trip expected to be dominated by the Syrian file and US-Turkish disagreements over Washingtons military support of the Kurdish units battling Turkey in northern Syria. Washington has expected tough talks between Tillerson and Turkish officials as Ankara has not been shy in expressing anger over Washingtons support for what it considers a Syrian extension to the outlawed Kurdistan Workers Party (PKK) and classified by Turkey, the US and the European Union as a terrorist organization. Washington recognizes the existence of ‘legitimate fears’ for Ankara, but at the same time calls for the need to reduce the number of victims to the maximum extent possible, and seeks to get Turkey to ‘determine its long-term intentions’ in Syria. Diplomatic sources told Asharq Al-Awsat that the US proposal to establish a 30 km deep security zone into Syrian territory on Turkeys border would be discussed, pointing out that Turkey first wants to ensure getting a clear position out of the US on the issue of stopping support to Kurdish units. US troops are not present in Afrin region at the moment-- therefore there is no concern over the possibility of a Turkish-US confrontation, the sources added. Both Ankara and Washington do not want a confrontation in Manbij. However, Turkey intends to launch a military operation if Kurdish units do not withdraw from posts along its borders. Sources considered that Washington, if it wants to prevent this confrontation, is likely to implement its previous commitments to withdraw Kurdish units to the east of the Euphrates River and cease its arms support. Turkey launched “Operation Olive Branch” on Jan. 20 to clear its borders of YPG militants, and has since increased its tone of criticism against the US. Manbij, a town in northwestern Syria, has become the focus of the growing bilateral spat.