Foreign Minister Mevlüt Çavuşoğlu and his U.S. counterpart Mike Pompeo held a phone call on Sunday evening, according to diplomatic sources.

The sources did not provide additional details as to the subject matter of the call.

On Saturday, Defense Minister Hulusi Akar told the U.S. delegation at the Munich Security Summit that Washington's support for the PKK's Syrian offshoot People's Protection Units (YPG) remains to be the biggest obstacle in relations between Turkey and the U.S. He emphasized that the area east of the Euphrates in Syria should be cleared of YPG terrorists, in order for a safe zone patrolled by Turkish forces to be established.

In December, U.S. President Donald Trump announced that the U.S. would withdraw its troops from Syria, saying that Daesh was defeated. Days after, President Recep Tayyip Erdoğan pledged that Turkey would take over the fight against the remnants of Daesh in Syria but put the likely operation east of the Euphrates against the YPG on hold.

Ankara and Washington have been at odds for some time now due to the latter's close partnership with the YPG. Turkey sees the YPG as an extension of the PKK, which has claimed the lives of more than 40,000 people its 30-year terror campaign against Turkey. The U.S., however, while listing the PKK as a terrorist group, opted to continue its steadfast militarily support for the terrorist organization under the pretext of fighting Daesh despite the warnings of its NATO ally.

On Friday, the White House said that Trump intends to nominate David Satterfield, a veteran diplomat with deep experience in the Middle East, to be U.S. ambassador to Turkey -- a post which has been vacant since October 2017.