IS bastion in Syria soon to be isolated: coalition

Islamic State's self-proclaimed capital, the Syrian city of Raqa, will soon be isolated from the rest of the world, a spokesman for the US-led coalition fighting the jihadist group.

Although it will not be completely encircled, "it will be very difficult to get into or out of the city," Colonel John Dorrian said in a video conference from Baghdad."

"What we would expect is that within the next few weeks the city will be nearly completely isolated," Dorrian said.

The coalition has been gradually tightening a vice on IS in Iraq and Syria.

US-backed Iraqi forces have recovered part of the Iraqi city of Mosul, although the city's western districts have yet to be retaken.

Raqa is the coalition's next big objective. Arab-Kurdish forces backed by the coalition have launched an offensive on Raqa, advancing on the city from the north.

But the issue of who exactly will assault the predominantly Arab city has not yet been worked out.

Turkey has expressed interest in taking part in the operation, with Turkish Foreign Minister Mevlut Cavusoglu indicating that his country is ready to deploy special forces to take part in the battle.

Turkey opposes giving added weight to the Syrian Democratic Forces, as the Arab-Kurdish coalition is called, regarding it as little more than a front for the Kurdish YPG militant group, which Ankara considers a terror organization.

"We have said for many months the US would be opened to a Turkish role," Dorrian said.

Turkey already has troops in northern Syria, having launched an offensive in the area in August against IS and Kurdish militants.

After a rapid advance, the Turkish army, which was acting in support of Syrian rebel groups, has been embroiled in recent weeks in deadly combat around Al-Bab, in northern Syria.