"We have agreed definitively with the (US-led) international coalition that there will be no role for Turkey or the armed factions allied with it in the operation," Talal Sello of the Syrian Democratic Forces (SDF) told AFP.

The SDF is an alliance led by the Kurdish People's Protection Units (YPG) and has been a key ally of the US-led coalition against IS.

But Turkey considers the YPG a "terrorist" group, and in August launched a military operation inside northern Syria targeting the Kurdish forces as well as IS.

The SDF announced Sunday it had begun a long-awaited operation to capture Raqa from IS, as Iraqi forces push into the jihadist group's bastion of Mosul across the border in Iraq.