The United States is sending 200 additional military personnel to Syria to help the campaign to drive the Islamic State militant group from Raqqa, U.S. Defense Secretary said on Saturday.

Speaking in Bahrain at the Manama Dialogue conference on Middle East security, Carter said the 200, including special forces trainers, advisers and explosive ordnance disposal teams, would join 300 U.S. special forces already in Syria.

He added in a speech that Russia, President Bashar al-Assad's top foreign military backer, had "only inflamed the civil war and prolonged suffering of the Syrian people."