US military chief: 12,000-15,000 Syrian rebels needed to retake eastern Syria

A Western-backed opposition force of around 12,000 to 15,000 would be required to retake areas of eastern Syria now controlled by Islamic State, the top US military officer said on Friday.

"Five thousand has never been the end state ... Twelve to 15,000 is what we believe they would need to recapture lost territory in eastern Syria," General Martin Dempsey, chairman of the Joint Chiefs of Staff.

Last week, Congress gave temporary approval to a plan for the United States to train members of Syria's moderate opposition to combat the Islamic State, which is seeking to expand its hardline rule from a base in eastern Syria. The initial number of opposition fighters to be trained by the United States is expected to be around 5,000.