US-Turkish relations have worsened over Washington's support for the Kurdish People's Protection Units (YPG), which Ankara considers a terrorist group but is a core US partner in the fight against the Islamic State.
Ankara views the YPG as the Syrian arm of the Kurdistan Workers' Party, a group it has been in armed conflict with for over three decades. Both the US and the EU consider the PKK a terror group.
Relations between Turkey and Washington eased after a recent visit by the now-former US Secretary of State Rex Tillerson. In it, the US and Turkey agreed to a joint administration of Manbij, an area where US forces are stationed.
Turkey's Operation Olive Branch in nearby Afrin, launched on 20 January, raised concerns that the two NATO members could come into direct conflict.
Turkish media has also seized on a July 2016 Mike Pompeo tweet - the incoming new Secretary of State - referring to Turkey as a "totalitarian Islamist dictatorship". The tweet has been deleted.
Turkey is also angered by the US' failure to extradite Fethulla Gulen, religious cleric and leader of the Gulen movement.
Ankara views Gulen and behind the failed July 2016 coup attempt in Turkey.
Source: The New Arab