BEIRUT -- Syria's increasingly powerful Islamist rebel factions rejected the country's new Western-backed opposition coalition and unilaterally declared an Islamic state in the key battleground of Aleppo, a sign of the seemingly intractable splits among those fighting to topple President Bashar Assad.
The move highlights the struggle over the rebellion's direction at a time when the opposition is trying to gain the West's trust and secure a flow of weapons to fight the regime. The rising profile of the extremist faction among the rebels could doom those efforts.
Such divisions have hobbled the opposition over the course of the uprising, which has descended into a bloody civil war. According to activists, nearly 40,000 people have been killed since the revolt began 20 months ago. The fighting has been particularly extreme in Aleppo, Syria's largest city and a major front in the civil war since the summer.
Salman Shaikh, director of The Brookings Doha Center in Qatar, said Monday that the Islamists' declaration will unsettle both Western backers of the Syrian opposition and groups inside Syria, ranging from secularists to the Christian minority. "They have to feel that the future of their country could be slipping away," he said. "This is a sign of things to come, the longer this goes on. The Islamist groups and extremists will increasingly be forging alliances and taking matters into their own hands."
The West is concerned about sending arms to rebels for fear that they could end up in extremists' hands. In Washington, State Department spokeswoman Victoria Nuland said that since the new opposition group has endorsed pluralism and tolerance, "it's not surprising to us that those who want an extremist state, or a heavily Islamist state, in Syria have taken issue with this."
The Islamists' announcement, made in an online video released Sunday, shows the competing influences within the rebellion, between religious hard-liners -- including foreign al-Qaida-style jihadi fighters -- who want to create an Islamic state in Syria and the newly formed Syrian National Coalition, created earlier this month in hopes of uniting the disparate groups fighting the Assad regime.
The National Coalition was formed under pressure from the United States, which sought a more reliable partner that nations could support. Key to its credibility is whether it can ensure the support of the multiple, highly independent rebel brigades battling on the ground within Syria, which largely ignored the previous opposition political leadership made up of exiles.
The new opposition bloc, formed Nov. 11 in Qatar, is trying to allay fears of extremism within the rebellion. A moderate cleric, Mouaz al-Khatib, was chosen as its leader in an attempt to establish the movement's religious credentials with the public while countering more radical factions.
In Cairo, Mr. Khatib played down the significance of those who reject the alliance, saying, "We will keep in contact with them for more cooperation in the interest of the Syrian people." He also announced that the coalition would be headquartered in the Egyptian capital.
The coalition is gaining some traction internationally. France was the first Western nation to recognize it as the only legitimate representative of the Syrian people. France also welcomed a member of the Syrian opposition as the country's ambassador. Turkey and the six-nation Gulf Cooperation Council also recognized the group as the representative of the Syrian people.
But the United States and Italy have been somewhat less forthcoming. President Barack Obama has said the U.S. needed more time and wanted to make sure that the group "is committed to a democratic Syria, an inclusive Syria, a moderate Syria."