BEIRUT — Al-Qaida's branch in Iraq and the most powerful rebel extremist group in Syria have officially joined ranks against President Bashar Assad to forge a potentially formidable militant force in the Middle East.
The merger of the Islamic State in Iraq and Jabhat al-Nusra forms a new entity that could be an even stronger opponent in the fight to topple Assad and become a dominant player in what eventually replaces his regime.
The new group, called the Islamic State in Iraq and the Levant, underscores the growing confidence and muscle of Islamist radicals fighting on the rebel side in Syria's civil war. It also bolsters the Syrian government's assertions that the regime is battling terrorists and that the uprising is a foreign-backed plot.
While the U.S. and its European and Gulf allies are concerned about the rising prominence of Islamists among the rebels, the merger is unlikely to prompt a shift in the international support. Late last year, Washington declared that Jabhat al-Nusra had ties to al-Qaida and designated it a terrorist organization.
To try to counter the rising influence of Jabhat al-Nusra and other Islamic extremists in the civil war, the U.S. and its allies have boosted their support for rebel factions deemed to be more moderate.
On the political front, they helped created the opposition umbrella group, the Syrian National Coalition, in the hope that it will serve as the united face of those trying to unseat Assad and administer much of the territory in northern Syria that rebels have managed to pry away from regime forces in the past year.
The U.S. and other countries also have stepped up covert support for rebels on the ground by helping to coordinate shipments of new weapons and training rebels in Jordan, officials say. Those receiving training are mainly secular Sunni Muslim tribesmen from central and southern Syria who once served in the army and police.
The force is seen as a counterbalance to the Islamic militant groups — chief among them Jabhat al-Nusra — that have proved to be among the most effective of the myriad rebel factions fighting Assad's forces, officials say.