Gains by al-Qaida linked Jabhat al-Nusra in northwestern Syria threatens to leave the U.S. with few options on the ground in that region.

Jabhat al-Nusra recently attacked and overran Harakat al-Hazm and the Syrian Revolutionaries Front (SRF) led by Jamal Maarouf, two key American aligned militias that the Obama administration saw as key parts of its strategy against the Islamic State (IS).

Maarouf fled to Turkey and no longer has any brigades in the area around Idlib, located in northwestern Syria near the Turkish border. He previously proclaimed his solidarity with Jabhat al-Nusra and the Islamic Front in a January Twitter post.

"The front of the Syrian revolutionizes, The Islamic Front, and Jabhat al-Nusra, Muhajreen and Ansar, we are all in the fighting front together against the regime. What happened now is a fitna (strife), God damn who ignited it," Maarouf wrote.

Al-Nusra also killed a commander belonging to the Free Syrian Army's Dawn of Freedom Brigades in the fighting.

Jabhat al-Nusra confiscated heavy gear and weapons that the West had provided to its allies.

The Islamist group decided to attack the U.S.-backed rebel groups after the Obama administration bombed its fighters and those belonging to IS. This decision also opened the way to an agreement between Al-Nusra and IS to cooperate in destroying Maarouf's faction.

President Obama said in September that a "moderate" force would be created and that their first targets were jihadists.

The U.S.-led coalition, along with "U.S. spies," aim to eliminate all Islamic factions that "do not comply with Western policy," Al-Nusra leader Abu Mohammed al-Golani said in the Al-Monitor story.

"We have made the decision to cancel the SRF," Golani said.

This opens the way for the al-Qaida linked group to carve out an Islamic emirate in the area around Idlib.

It hopes that such an emirate would increase its credibility among global jihadists and compete with the Islamic State to attract new fighters. Jabhat al-Nusra already has created its own courts in towns surrounding Idlib, an area isolated from direct contact with Assad's forces and from those with the Islamic State.

The U.S.-aligned rebels blamed the Obama administration for their failures. Although President Obama promised to arm the "moderate" Syrian rebels to fight the Islamic State and the Assad regime, supplies trickled in, slowed in part by bureaucracy.

"We decide on the mission that we want to do. Then we apply to the operations room for the weapons. If they agree with our military plan, some weapons arrive," a commander calling himself Abu Ahmed told the Daily Telegraph. "If we receive TOW anti-tank missiles, we have to film every time we use one to prove we haven't sold it on."

Abu Ahmed also complained that other FSA units didn't come to help, fearing Al-Nusra would attack them too.

The U.S.-backed rebels have also witnessed a stream of defections to Al-Nusra and IS.