BAGHDAD, Iraq – Car bombs killed six policemen and wounded 15 in new attacks on Iraq’s security services yesterday as political factions wrangled over putting together a government.

The Shiite Muslim-dominated United Iraqi Alliance and a Kurdish coalition, which emerged from the January 30 elections with the two biggest blocks of seats in the National Assembly, made little headway in their talks on combining forces to select the leaders of the new government.

Meanwhile, Ayad Allawi, the interim prime minister whose party finished third, denied rumors he had given up his effort to stitch together support from other groups, including the Kurds, that would allow him to remain prime minister.

Forming Iraq’s first democratically elected government is a key step in the American plan for stabilizing the country, and insurgents have been striking at Iraqi police and military forces seeking to undermine the effort.

Two suicide car bombs exploded outside the Interior Ministry in eastern Baghdad and killed at least five policemen and wounded nine, the defense ministry reported.

Another car bomb targeted a police convoy in Baqouba, 35 miles northeast of the capital, and killed one Iraqi policeman and a civilian, the American military said. Six officers and 10 civilians were injured. In the north, insurgents blew up a natural gas pipeline between Kirkuk and Dibis, about 20 miles away. Officials said the blast would reduce gas production, but could not immediately say by how much.

Violence that has killed hundreds of people the past three weeks led Mr. Allawi to extend a state of emergency until the end of March. First announced nearly four months ago, the order affects all of Iraq except Kurdish-run areas in the north. The emergency decree includes a nighttime curfew and gives the government extra powers to make arrests without warrants and launch police and military operations when it deems necessary.

The American military reported that three American soldiers were killed in action Wednesday. The military said two soldiers were mortally wounded when a roadside bomb struck their vehicle in Baghdad. Another soldier was killed in Babil province.

More than a month after the elections, negotiations between the cleric-supported United Iraqi Alliance and the coalition of Kurdish parties are struggling and plans for convening the 275-member National Assembly this week have been suspended.

The United Iraqi Alliance won 140-seats and wants the leader of its Islamic Dawa party, Ibrahim al-Jaafari, to be the next prime minister. But it needs the support of 42 other deputies to elect a president – the first step in selecting a prime minister.