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 United States 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, the allies have boosted their support for rebel factions deemed to be more moderate.

advertisement | advertise on newsday

On the political front, they helped create the opposition umbrella group, the Syrian National Coalition, in the hope it would 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.

In an article yesterday in The Washington Post, Iraqi Prime Minister Nouri al-Maliki warned that a Syria controlled by al-Qaida and its affiliates "would be more dangerous to both our countries than anything we've seen up to now." He added that such a scenario "grows more likely by the day."