General: ISIS campaign has killed 8,500 fighters

The U.S. military campaign against the Islamic State in Iraq and Syria (ISIS) has killed 8,500 enemy fighters so far, the commander overseeing the effort said Tuesday.

"Make no mistake, [ISIS] is losing this fight," said Army Gen. Lloyd Austin, commander of U.S. Central Command at a House Armed Services Committee hearing on Tuesday. 

The last update officials gave on enemy fighters killed came in late January, when officials said more than 6,000 ISIS fighters have been killed. 

Austin also said the coalition has destroyed hundreds of ISIS's vehicles, along with tanks and heavy weapons systems. 

"We've significantly degraded his capability, his ability to command and control his forces. And also, his primary sources of revenue namely, his oil refineries and his crude collection points," he added. 

Austin acknowledged reports that ISIS has been trying to spread to North Africa but said it was because the group was losing ground in Iraq and Syria. 

The U.S. has led a six-month military effort against ISIS involving U.S. and coalition member airstrikes in Iraq and Syria, training 12 brigades of Iraqi forces, and training and equipping moderate rebels in Syria to fight ISIS there on the ground. 

Austin said the U.S. would begin training the moderate Syrian rebels later this month, in what is expected to take eight to 12 months to produce 5,000 fighters to take on ISIS and pushback against the Syrian regime. 

He also touched on what's seen as a weakness in the administration's strategy against ISIS — the lack of clarity over its policy toward Syria and its leader, Bashar Assad. 

Austin said the U.S. needs to "first get things under control in Iraq ... before expanding efforts to Syria." If the U.S. does that, "I believe that we can and believe that we will be successful."