White House Press Secretary Jay Carney on Monday called on the international community to unite in order to isolate and topple Syrian President Bashar Assad.

Each day the Assad regime is in power, Israel’s Army Radio quoted Carney as saying, the chance that violence will spread to Syria’s neighbors grows.

“As evidenced by the very massacres that the Assad regime participated in and is now denying, the sooner that political transition takes place, the better for the people of Syria, and the better the chances that a bloody sectarian war will be avoided,” Carney said. ”The longer that Assad continues to essentially wage war on his own people… brutally murder, execute his own people, the greater the chance that that situation will dissolve into a sectarian civil war and will spill over its borders and cause instability in the region.”

Also on Monday, Syrian activists announced a new rebel coalition that aims to overcome deep divisions within the opposition in its fight against the forces of Assad.

The group, the Syrian Rebels Front, declared its formation in a news conference in Turkey that had the hallmarks of a public relations event, including a banner, video presentations and a simultaneous translation service. But it was uncertain how the new organization would coordinate with other sectors of the Syrian opposition, whose failure to unite has hobbled its campaign to topple Assad despite a nationwide uprising that has lasted more than one year.

Khaled al-Okla, one of the organizers, said the fledgling group will coordinate with the Free Syrian Army, a loose coalition of rebel units whose nominal leaders are based on the Turkish side of the border with Syria. Members of the Free Syrian Army acknowledge its commanders have limited or no operational control over rebel units inside Syria, but they say the label has given a public face to the lightly armed factions, who are under heavy pressure from government forces with tanks and artillery.

“We might have some treaties or agreements to coordinate our work in Syria,” said al-Okla, who claimed his umbrella group has 12,000 fighters. He also read a statement that said the Syrian Rebels Front had been formed in light of Assad’s “scorched earth policy” as well as “the failure of all Arab and international initiatives to rein in Assad from his crimes,” suggesting the rebels were giving up on a peace plan proposed by UN envoy Kofi Annan. The 15-month-old revolt against Assad’s rule has killed up to 13,000 people, according to activist groups.

The Syrian rebel statement said the launching of the new front could serve “as the melting pot that brings together all armed rebel factions across Syrian territory as they seek to topple the criminal regime.”

However, some in the audience, which included journalists, were skeptical. One person took a microphone and asked: “Why do we need a new front? There are already a lot of fronts.”