The United States secretary of state, Rex Tillerson, is in Turkey where he aims to alleviate rising tensions with Turkey over the Syrian conflict.
Diplomatic disputes have risen since Turkey initiated a military offensive into northern Syria in January, aiming to eliminate Kurdish Syrian Democratic Forces (YPG) militants, some being part of a US-supported armed coalition.
Turkey believes the Syrian Democratic Forces to be an extension of the banned Kurdistan Workers Party (PKK), which waged a lengthy war against the Turks 30 years ago.