Baghdad, Iraq ? U.S. and Iraqi troops repelled a series of coordinated attacks including suicide car bombs, killing six insurgents and capturing 12, in southern Baghdad, the military said Saturday.

In political developments, Sunni Arabs on the committee drafting a new constitution rejected Kurdish demands for federalism as long as foreign forces remain in Iraq. The statement came on the eve of a meeting to try to overcome differences on the charter.

Iraq’s most feared terror group, meanwhile, warned Sunni Arabs that voting in a referendum on the charter this fall would be tantamount to rejecting Islam.

The fighting erupted about 8 p.m. Friday when guerrillas opened fire on an Iraqi army position, the American military said. U.S. attack helicopters responded with rockets and gunfire.

At nearly the same time, a suicide attacker drove a truck loaded with explosives into a nearby Iraqi army checkpoint, killing an Iraqi soldier. A second suicide driver tried to attack another Iraq position in the area, but a U.S. tank opened fire and the car detonated prematurely.

Minutes later, insurgents at a fourth location fired two rocket-propelled grenades and a mortar round at another Iraqi army post in southern Baghdad. None of the rounds caused any damage, the U.S. statement said.

Over the next two hours, insurgents tried to launch further attacks on the two Iraqi army posts but were driven off by U.S. and Iraqi fire, the statement added.

U.S. troops suffered no casualties, but six insurgents were killed and 12 were captured in the fighting, according to the military.

In recent weeks, U.S. officials have said the insurgents had started using so-called “swarm” tactics – coordinating multiple attacks and firing from several locations – against coalition forces.

Separately, the U.S. command said an American soldier assigned to a unit in the northern city of Mosul was killed in action Thursday “during a terrorist attack” there. No further details were given.

At least 1,827 members of the U.S. military have died since the Iraq war began in March 2003, according to an Associated Press count.

The Bush administration is hoping that progress on the political front will help curb the insurgency by luring Sunni Arabs away from rebel ranks. Key to maintaining the momentum is a new constitution, which must be approved by parliament by Aug. 15 and by voters in a referendum two months later.

Sunni, Shiite and Kurdish political leaders planned to meet today to try to overcome differences that have deadlocked the work of a 71-member committee charged with writing the constitution.

Those differences include federalism, the role of Islam, a description of national identity and the distribution of wealth.

On Saturday, Sunni Arab members of the drafting committee rejected Kurdish demands to transform Iraq into a federal state, saying such a step should not be taken during foreign military occupation and an unstable security situation.

The Sunni delegates believe federalism should be discussed in the future when there is a parliament that represents all Iraqis, member Kamal Hamdan said.

Most Kurds and some Shiites are for a federal system, but Sunni Arabs have opposed the idea, fearing it could lead to the breakup of Iraq.