Only four or five U.S-trained Syrian fighters remain on the battlefield against Islamic State militants, the top U.S. commander in the Middle East acknowledged Wednesday in the face of withering criticism from senators who dismissed the training program as a "total failure" and demanded a change of strategy.

Gen. Lloyd Austin told the Senate Armed Services Committee that the U.S. is looking at better ways to deploy the Syrian forces, but he agreed that the U.S. will not reach its goal of training 5,000 in the near term.

The first group of 54 U.S.-trained Syrian fighters was sent into Syria in late July. But a Syrian affiliate of al-Qaida attacked the group, killing several of the fighters and reportedly taking others hostage. A number of the remaining fighters fled.

Until now, the U.S. has declined to say how many of that group of trained Syrian rebels remained in the fight. And Austin's revelation that it's only a handful only further inflamed the lawmakers' criticism.

The committee's chairman, Republican Sen. John McCain, called the U.S. strategy against Islamic State in Iraq and Syria a debacle. He said assessments by Austin and Pentagon that the U.S. strategy is working is "divorced from reality."

And other senators focused directly on the stumbling training effort that takes months to identify and screen Syrian rebels for the program and has lagged far behind original goals.

"We have to acknowledge this is a total failure," said Sen. Jeff Sessions, R-Ala., said about the training. "I wish it weren't so, but that's the fact."

Congress has approved $500 million to train Syrian fighters. Officials have said fewer than 200 are going through training now.

Austin urged patience, saying that over time the trained Syrian fighters will be able to join other rebel groups fighting along the Syrian border.

Christine Wormuth, undersecretary of defense for policy, told senators that the U.S. is looking at how to speed up the recruiting and screening processes. But she said the current criteria for selecting rebels for the program is in line with what Congress initially authorized.

One of the problems has been that many Syrian fighters want training and equipment to fight the government forces of President Bashar Assad, but the U.S. program is limited to rebels who agree to only battle the Islamic State group.