U.S.-backed rebels in Syria are severely overmatched and on the brink of being wiped out by the combined forces of an al Qaeda branch and the Islamic State group, the Associated Press reported. The Jabhat al-Nusra, al Qaeda’s branch in Syria, and the Islamic State group, which were once fighting one another, have turned their efforts against rebels backed by Western powers.

The U.S.-backed rebels are now facing a two-headed assault by the extremist groups, which activists say are increasingly working together to eliminate them, Reuters reported. The militants have assassinated some of the U.S.-backed rebels’ top commanders. Some of the rebel fighters have been forced to surrender, while others have defected to the side of the extremists.

“This is the end of the Free Syrian Army,” Alaa al-Deen, an opposition activist in Idlib, told AP. “It’s the beginning of an Islamic emirate.”

According to a Syrian opposition official quoted by AP, a truce was agreed upon at a meeting between leaders of al-Nusra and the militant group formerly known as ISIS Nov. 2. The meeting, held in the town of Atareb -- nearly 20 miles west of Aleppo -- was also attended by militants of the Khorasan Group, al Qaeda militants from Afghanistan and Pakistan, and members of the Syrian rebel group Ahrar al-Sham.

Washington announced this summer it had plans to arm moderate Syrian rebel forces in an effort to fight the Islamic State group, but the move is still awaiting congressional approval, AP reported. The U.S. has acknowledged giving nonlethal aid to rebels, and officials have said U.S. weapons have reached the hands of factions vetted by Washington. Meanwhile, the CIA has said it is running a training program in Jordan.

The Islamic State group and Nusra Front have come together at least in part as a response to U.S.-led airstrikes that targeted both groups in the region, several activists told AP. Al-Nusra has been hit three times in strikes the U.S. has said were aimed at a secret cell of high-ranking al Qaeda militants plotting attacks.

“There was hope that [the U.S.-backed rebels] might prove to be an effective force in the crackdown on the al Qaeda presence in Syria -- but that has been dashed,” Aymenn al-Tamimi, an expert on rebel groups, told AP. “They are not strong enough.”