Turkish President Recep Tayyip Erdogan has claimed the US reneged on a promise to remove Kurdish YPG forces from Manbij. The mostly-Kurdish People's Protection Units have formed the backbone of the coalition's partnered ground forces.
Turkey considers the YPG to be the Syrian extension of the PKK, a named terrorist organization by Turkey, the United States, and the European Union.
France, as part of the coalition, has offered to mediate between the Kurdish group and Ankara.
Turkey rejected the offer.
“Who are you to talk about mediation between Turkey and a terror group?” said Erdogan on Friday.
AFP photojournalist Delil Souleiman, who has embedded with Kurdish and coalition forces through the ISIS conflict, reported on Tuesday that tensions are high between Turkish and coalition-backed forces in northern Syria.
"We're on high alert. There are always skirmishes at night," Kurdish fighter Shiyar Kobane said. "They fire mortar rounds and shell our positions."
Turkey has a presence in nearby Jarabulus and al-Bab.