US-backed Kurdish and Arab fighters today announced a new phase in their campaign for the Islamic State group's Syrian stronghold of Raqa. A spokeswoman of the Syrian Democratic Forces (SDF) said the third phase aims at liberating Raqa and its surroundings. <br/><br/>It launched the campaign to capture the city last November and have taken some ground further up the Euphrates Valley but are still some distance away. Washington has dispatched about 500 troops including bomb disposal experts, trainers and special operations troops to support the campaign. <br/><br/>Pentagon and alliance officials said Washington has also provided SDF with armoured sports utility vehicles since President Donald Trump took office.