New U.S. mission in Iraq aims to integrate troops, Sunni tribes

"The Sunnis want to be part of the fight," the official said on condition of anonymity.

The official said additional U.S. forces sent to Iraq would be more focused on advisory roles than training. Reuters has previously reported that around 400 additional U.S. troops would be deployed.

(Reporting by Phil Stewart; Editing by Doina Chiacu)