Syrian force fighting for Raqa is mainly Arab: US official

The US-backed Arab-Kurdish alliance leading the offensive to surround and recapture the Islamic State group's main bastion in Syria now comprises mainly Arab fighters, a US official said Wednesday.

The development is significant because the United States has been trying to bolster the Arab part of the Syrian Democratic Forces in a bid to placate Turkey, which views the Kurdish component as terrorists.

The SDF since last fall has been ramping up an offensive to recapture Raqa, which IS views as the capital of its supposed "caliphate."

The alliance is being backed by US-led air power, and American and other Western commandos are training and advising local forces.

"About 75 percent of that force that is now isolating Raqa is Syrian Arab, and this is a reflection that's demographically fairly consistent with what you would find in that area," US military spokesman Colonel John Dorrian told reporters.

Still, he said he expected Kurdish fighters to be involved in liberating Raqa "at some level."

Turkish forces are operating in northern Syria and have joined the anti-IS fight, but are also working to keep the Kurdish fighters in check.

Dorrian said it is possible Turkish forces may play a role in Raqa.

"We haven't come to an agreement about what that role will be or if there will be one, but we talk to Turkey... every day," he said.