Last week the Al Nusra Front, the military backbone of the US-sponsored Syrian opposition, openly swore its loyalty to Al Qaeda.

Al Nusra leader Abu Mohammed al-Golani pledged allegiance to Al Qaeda leader Ayman al-Zawahiri, the Egyptian-born cleric who served for many years as Osama bin Laden’s second-in-command.

“The sons of Al Nusra Front pledge allegiance to Sheikh Ayman al-Zawahiri,” al-Golani said in a recorded message released last week. The statement also indicated that the Syrian terrorist group would merge with Al Qaeda in Iraq, from which Al Nusra has received personnel and training.

Abu Bakr al-Baghdadi, the head of the Islamic State in Iraq, Al Qaeda’s affiliate in that country, said last week that his group would join with Al Nusra under the shared banner of “The Islamic State in Iraq and the Levant.”

The Al Nusra Front (or Jabhat al-Nusra) became the most effective armed group in the US-backed Syrian opposition last year. Its cadres, Islamist militants recruited internationally with combat experience from other wars, have inflicted several defeats on Syrian government forces, while carrying out sectarian atrocities against minority groups and alleged regime sympathizers.

The Free Syrian Army (FSA), the loose coalition of militias sponsored by Washington and its allies in their proxy war against the government of President Bashar al-Assad, issued a statement disavowing any formal ties with Al Nusra.

“We don’t support the ideology of Al Nusra,” an FSA spokesman said. “There has never been and there will never be a decision at the command level to coordinate with Al Nusra.”

This denial appears meaningless, however, as the FSA then admitted that it planned to continue co-operating with Al Nusra fighters on “certain operations.”

Without Al Nusra, the FSA would have very limited fighting capabilities. In July 2012, the UK-based Guardian newspaper reported from within Syria that the FSA frequently relied on al-Nusra when fighting the Syrian army. In the piece, titled “Al-Qaeda turns tide for rebels in battle for eastern Syria,” FSA personnel said that they had called upon Al Nusra to carry out truck and car bombings, plant roadside bombs, and to supply fighters, small arms and ordnance.

The FSA lacks a popular base of support, and appears to have little operational authority, within Syria. Rather, it is various sectarian and ethnic-based militias that carry out strikes against the Syrian regime, each for their own ends. Among these groups, it is Al Nusra that has proved to be the most deadly. Its militants, drawn to the Syrian war under the banner of Islamist jihad, are recruited from the ranks of Sunni extremist veterans of the wars in Chechnya, Iraq, Afghanistan, and Libya.

Its shadowy leader, al-Golani (his nom de guerre ), is believed to have been a fighter in the Al Qaeda-linked insurgency in Iraq during the US occupation and subsequent ethno-sectarian civil war in that country.

Al Nusra has claimed responsibility for the overwhelming majority of suicide bombings inside Syria, including the December 2011 twin-suicide attack in Damascus that killed 49 people and injured over 160 others, the May 2012 bombing in the capital in which 55 people died and some 400 were wounded, and a triple suicide attack in Aleppo in October, which killed 48. In all these atrocities, and hundreds of other attacks carried out by the group over the past fifteen months, the majority of casualties have been civilians.

Al Nusra’s formal declaration of solidarity with Al Qaeda thus comes more as an inconvenience than a surprise to the Obama administration and its allies.

Islamist militias, including those associated with Al Qaeda, have received hundreds of millions of dollars in cash and materiel from Saudi Arabia, Qatar, and other US-backed forces—all under the watchful eye of the CIA, whose agents oversee the flow of supplies to the Syrian opposition across the borders of Turkey and Jordan.

On Thursday, the Assad government called on the UN to designate Al Nusra as a terrorist organization, like Al Qaeda. In a letter to the UN Security Council, the Syrian foreign ministry claimed that the announced merger confirmed previous assertions by Damascus that Al Nusra is engaged in terrorist crimes against the Syrian people.

The letter to the Security Council criticized the efforts within the “international community” to prevent Al Nusra from being branded as a terrorist organization, with the Assad regime attempting to put diplomatic pressure on US allies, such as Saudi Arabia and Qatar, which have sponsored the Islamist fighters.

Washington was compelled to officially blacklist Al Nusra as a terrorist group in December. The designation came in the context of the establishment in November 2012 of a new US-sponsored anti-Assad umbrella group, the National Coalition for Syrian Revolutionary and Opposition Forces. Al Nusra was hostile to this group, which includes moderate Sunnis as well as secular and Kurdish personnel.

The terrorist label applied to Al Nusra by the Obama administration was mainly symbolic, however. In the months since the designation, al-Golani’s fighters have proven themselves even more capable of striking at Syrian regime targets and carrying out terrorist attacks.

On December 23, al-Nusra declared a “no-fly zone” over the city of Aleppo, the main commercial center of Syria prior to the civil war. According to Al Jazeera, the group was able to deploy 23mm and 57mm anti-aircraft guns against Syrian armed forces aircraft, as well as civilian planes that were suspected of carrying government personnel or supplies.

Al-Nusra has emerged as the principal opposition group in the battle for control of Aleppo, which lies close to the Turkish border and the large US Air Force base at Incirlik. It regularly fights off Syrian government assaults on rebel-held areas.

Given the extensive presence of the US military and the CIA in and around Syria, and Washington’s influence within the despotic Persian Gulf sheikhdoms that bankroll the opposition, it is inconceivable that Al Nusra or similar outfits could function without tacit support from US imperialism.

Secretary of State John Kerry effectively acknowledged that the US would turn a blind eye to the arming of al-Nusra during a press conference last month with Hamad bin Jassim bin Jaber al-Thani, a Qatari royal. Kerry insisted that Washington was doing everything to ensure that support went to the “right people” in the Syrian opposition. He added, however, that there could be “no one hundred percent guarantee” that the flood of arms and money coming into Syria from the US and its allies would not end up in the hands of the local branch of al-Qaeda.