The US military is gradually expanding a new program to train and equip Syrian opposition fighters, but building a force that can effectively take on Daesh terrorist group may take longer than expected, Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, has said.

He said the training course would be a success if the US was able to recruit, vet and train enough fighters who will form the new, moderate Syrian rebel force.

“That’s going to be a challenge and may take longer than we think,” he said in an interview.

In May, the Pentagon launched the long-awaited effort when it began training an initial class of about 90 fighters in Jordan.

A senior military official said that the US military had begun working with a second class of about 50 Syrian fighters in Turkey in mid-May.