1.The US and Turkey likely failed to overcome their strategic divide during a meeting between US President Donald Trump and Turkish President Recep Erdogan on May 16.
2.The current friction between the US and Turkey extends beyond operational disagreements over the anti-ISIS operation in Ar-Raqqa City. Turkey's strategic objectives diverge from those of the US in key ways. Turkish President Recep Erdogan ultimately seeks to reassert Turkey's status as a regional power throughout the sphere of influence of the former Ottoman Empire. Erdogan promotes the spread of Islamism across the Middle East and North Africa as a means to create governments responsive to him and his Islamist Justice and Development Party (AKP).
3.His aspirations drive an independent regional policy that eschews traditional partnerships with the US and Europe. He also leverages tools of the state to consolidate his increasingly authoritarian rule at home. These objectives - and the manner in which he pursues them - undermine the strategic goals of the US in the Middle East and Europe. Erdogan's distinct brand of 'Neo-Ottomanism' leads him to support Salafi-Jihadist Groups such as Ahrar al-Sham that serve as a vector for al Qaeda.
4.His embrace of populist nationalism fuels an active conflict with the Kurdistan Workers' Party (PKK), which is waging an insurgency in Turkey. The PKK's Syrian branch - the Syrian Kurdish People's Protection Units (YPG) - is the primary anti-ISIS ground force partner for the United States. Erdogan's attempts to forge an independent foreign policy prompt him to pursue superficial yet deepening ties with Russia and Iran.
5.Trump on May 16 reiterated his support for Turkey in the "fight against terror groups" including as ISIS and the PKK but did not address his recent decision to directly arm the Syrian Kurdish YPG. Erdogan condemned the decision as an "absolutely unacceptable" measure that presented a "clear and present danger" to Turkey. Erdogan also reiterated his calls for the US to extradite exiled cleric Fethullah Gulen. The White House likely offered greater cooperation with Erdogan against the PKK in Turkey and Northern Iraq to mitigate the risk of an imminent rift with Turkey. These efforts nonetheless remain insufficient to reverse the growing strategic divergence between the US and Turkey. (Source : ISW report)