President Barack Obama at the Pentagon
President Barack Obama at the PentagonReuters

President Barack Obama has authorized the use of airstrikes to defend U.S.-trained Syrian rebels if they come under attack from terrorist groups or the Assad regime, Bloomberg reported on Sunday.

The broader U.S. rules of engagement, approved July 31, came after rebels fighting Islamic State (ISIS) were attacked by the Al-Nusra Front, Syria’s Al-Qaeda affiliate, in northern Syria, a U.S. defense official said.

On Sunday, Al-Nusra posted a video purportedly showing its capture of the rebel force it accuses of aiding U.S.-led airstrikes against its fighters. 

The United States provided close air support to protect the rebels and quash the attack, he said, according to Bloomberg.

While airstrikes remain limited to Islamic State targets for offensive operations, they can now be used to defend U.S. allies on the ground in Syria, said the official, who spoke on condition of anonymity to discuss private deliberations.

The official discounted the risk of an American confrontation with the regime of Syrian President Bashar Al-Assad, should he choose to attack any American-trained forces on the ground.

The U.S.-trained rebels, who number about 60, have pledged to fight only Islamic State, not the Assad government, and Assad must focus on other threats to his regime, the official told Bloomberg.

Alistair Baskey, a National Security Council spokesman, said U.S.-trained rebels “are being provided with a wide range of coalition support” that includes defensive strikes.

While declining to discuss the specific rules of engagement, Baskey said the administration has “said all along that we would take the steps necessary to ensure that these forces could successfully carry out their mission.”

Obama’s move was first reported Sunday by the Wall Street Journal.

The new rules follow an agreement reached with Turkey last week that allows U.S. forces to use Turkey’s Incirlik airbase to launch airstrikes in Syria.

Turkey has sought U.S. assurances that it would protect allied ground forces, although the defense official said the new rules had no connection to the Incirlik accord.

Republicans in Congress, led by Senate Armed Services Chairman John McCain, have pushed the administration for months to assure Syrian rebels that the U.S. would come to their defense if needed in the fight against Islamic State.

McCain recently blasted the White House's military strategy against ISIS, suggesting the United States was "losing" the fight, and criticizing the pace of training for Syrian rebels.