The United States has decided to use airstrikes to defend Pentagon-backed Syrian rebels from attackers, including forces loyal to Syrian President Bashar Assad, U.S. officials reportedly said Sunday. The move has raised concerns that the U.S. military may come into direct conflict with government forces in Syria.

Although the decision by U.S. President Barack Obama is aimed at protecting Syrian fighters -- armed and trained by the U.S. -- to take on the Islamic State group militants, not forces loyal to Assad, the Pentagon is ready to provide defensive support to the rebels to fend off all kinds of attackers, the Wall Street Journal reported, citing unidentified U.S. officials.

“For offensive operations, it’s ISIS only. But if attacked, we’ll defend them against anyone who’s attacking them,” a senior U.S. military official told the Journal. “We’re not looking to engage the regime, but we’ve made a commitment to help defend these people.”

The Obama Administration has made clear that it would “take the steps necessary to ensure that these forces could successfully carry out their mission,” while support to the U.S.-backed fighters would include “defensive fires support to protect them,” Alistair Baskey, a White House National Security Council spokesman, told the Journal, without providing further details.

Syria-rebel-fighters Rebel fighters aim their weapons as they demonstrate their skills during a military display as part of a graduation ceremony at a camp in eastern al-Ghouta, near Damascus, Syria July 11, 2015. The newly graduated rebel fighters, who went through military training, will join the the Free Syrian Army's Al Rahman legion. Photo: Reuters/Bassam Khabieh

The U.S. has so far downplayed the idea that Assad’s forces would launch an offensive against the Syrian rebels. However, a sudden attack on the first batch of U.S.-trained forces by al Qaeda-linked fighters in northern Syria Friday might have triggered the first-known U.S. airstrikes to support them, Reuters reported, adding that the new rules will not apply to forces backed by the U.S. in southern Syria.

“We recognize, though, that many of these groups now fight on multiple fronts, including against the Assad regime, (Islamic State) and other terrorists,” Commander Elissa Smith, a Pentagon spokeswoman, told Reuters, adding that the U.S. military's program in Syria focuses “first and foremost” on fighting ISIS.

Pentagon launched the training program in Syria in May, with an aim to coach up to 5,400 fighters a year. However, the process of hiring and training local troops is said to have been slow with many candidates being declared ineligible.