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The Obama administration is preparing a major overhaul of its failed effort to train thousands of moderate Syrian rebels to fight the Islamic State group, shifting from preparing rebels for frontline combat to a plan to embed them with established Kurdish and Arab forces in northeastern Syria, U.S. officials said.

Instead of fighting the Islamic State in small units, the U.S.-trained rebels would be attached to larger existing Kurdish and Arab forces. They would be equipped with U.S. communications gear and trained to provide intelligence and to designate IS targets for airstrikes in coordination with U.S. troops outside of Syria, the officials said.

The change amounts to an acknowledgement that the administration's current approach is not working. It was described by officials who spoke on condition of anonymity because a final decision on how to proceed has not been made.

The discussion of a new approach comes a day after the head of U.S. Central Command, Gen. Lloyd Austin, told Congress that the $500 million effort to train 5,000 moderate Syrian rebels in a year had yielded "four or five" new fighters after another 50 or so were captured, wounded or fled in their first encounter with extremist militants.

The new approach is designed to intensify military pressure on Raqqa, the self-declared capital of the so-called caliphate the Islamic State has established across much of Syria and Iraq. The city is sometimes targeted by American-led coalition airstrikes, and Syrian government forces have occasionally targeted it as well.

In addition to changing the role of the U.S.-trained rebels, the Pentagon would scale back their numbers from the original target of 5,400 per year to a much smaller total, perhaps 500, the officials said. Their vetting, designed to weed out terrorist infiltrators, also would be streamlined, one official said Thursday.

Pentagon press secretary Peter Cook told reporters Thursday that officials are looking to make "adjustments," adding, "We're asking a host of questions about this program." He said the plan is for it to continue "in some form or fashion." He was not more specific.

Austin, who leads the anti-Islamic State campaign, told a Senate committee Wednesday that only four or five U.S.-trained rebels are currently operating inside Syria. That compares to the administration's original goal to train and equip 5,000 fighters by the end of this year.

Austin's disclosure triggered an avalanche of caustic comments. Sen. Kelly Ayotte, a New Hampshire Republican, called it "a joke." Sen. John McCain, R-Ariz., said it was further proof that the administration's counter-IS strategy is an "abject failure."

In remarks on the Senate floor Thursday, Sen. Deb Fischer, R-Neb., said the program's collapse could have been predicted.

"I wish I could say the complete failure of this strategy comes as a surprise. Unfortunately, it does not," she said.

In light of Austin's admission, Cook was asked Thursday whether Defense Secretary Ash Carter was considering firing the four-star Army general. Cook said Carter has "full confidence" in Austin.

At Wednesday's hearing, Austin and the Pentagon's policy chief, Christine Wormuth, made oblique references to altering the train-and-equip program, which Congress authorized last December with $500 million in funding.

Saying the program "has gotten off to a slow start," Austin said he was considering "the best means to employ these forces as we go forward," taking into account lessons learned from having sent an initial group of 54 U.S.-trained rebels into Syria in late July only to have them immediately attacked by al-Nusra, a Syrian al-Qaida affiliate. That debacle led to an administration review of the program and the current proposal to scale back the rebels' combat role.

Wormuth cited the prospect of using the U.S.-trained moderate rebels to "enable" the efforts of the Syrian Kurds, who already are coordinating with U.S. forces outside of Syria, as well as a group she called the Syrian Arab Coalition. The thinking is that the Syrian Arab force, which Wormuth called "very effective" in northeastern Syria, is in the best position to put heavy pressure on Raqqa.

Austin said Kurds coordinating with Sunni Arabs in northeast Syria near the Turkish border have retaken more than 17,000 square kilometers of terrain from the Islamic State over the past several months.

"The effects that they have achieved serve to create significant opportunities that, if pursued, could prove devastating for the enemy," the general said.