BAGHDAD, Iraq -- A pair of suicide car bombers killed 14 people Sunday in the biggest insurgent assault in months on the main road to Baghdad's airport, and other attacks killed a dozen more Iraqis and two American soldiers elsewhere in the capital.

A weekend of stepped-up violence across Iraq, which included six attacks on small Shiite Muslim shrines and the bombing deaths of two British soldiers near recently restive Basra late Saturday, came as politicians again failed to agree on a new Cabinet.

There had been hope that Prime Minister-designate Nouri al-Maliki would fill at least some Cabinet posts when parliament convened Sunday in Baghdad's heavily guarded Green Zone, perhaps even taking on for himself contentious roles such as the interior and defense ministries.

Al-Maliki's mandate to form a Cabinet expires May 22. Should he fail to do so, President Jalal Talabani would have 15 days to name a new nominee to try to form a Cabinet. The constitution is unclear on whether he could pick al-Maliki again.

Lawmakers have struggled since Dec. 15 parliamentary elections to put together a national unity government, which many Iraqis and the U.S. government hope will lessen sectarian tensions and undermine support for the Sunni Arab-dominated insurgency.

The negotiations have bogged down in squabbles over the allocation of key Cabinet jobs, unable to bridge sectarian and political divisions.

As the 275-member parliament convened, a party loyal to firebrand Shiite cleric Muqtada al-Sadr threatened to propose its own Cabinet list if other groups did not scale back their demands for roles in the new government.

Legislator Bahaa al-Araji of the United Iraqi Alliance denounced what he called U.S. meddling in the talks and set a deadline of two days to settle the matter. But the Shiite bloc has only 130 parliament members, which isn't enough votes to seat a Cabinet.

A coalition of three Sunni Arab parties holding 44 seats warned that it would withdraw from the political process if it did not get at least one key post such as the Defense Ministry.

That threat came several days after Shiite party with 15 lawmakers pulled out of the Cabinet talks because it was not given the Oil Ministry.

The surge in violence came one day before the resumption of Saddam Hussein's trial after a three-week break. The deposed leader and seven co-defendants are on trial for the killings of 148 people from Dujail after a 1982 assassination attempt in the town against Saddam.

The U.S. command said a roadside bomb just after dark Sunday killed two U.S. soldiers in east Baghdad. The military gave no other details on the deaths. At least 2,439 U.S. military personnel have died since the Iraq war began in 2003, according to a count by The Associated Press.

Late Saturday, a roadside bomb killed two British soldiers and wounded one as they patrolled in an armored vehicle near the southern city of Basra, Britain's Ministry of Defense said. A total of 111 British military personnel have died.

Baghdad's deadliest attack Sunday involved the twin suicide car bombs that exploded near a main checkpoint on a four-lane road leading to Baghdad's international airport. The blasts killed at least 14 Iraqis and wounded six.

Twelve other Iraqis were killed in Baghdad by four roadside bombs, three that targeted Iraqi police patrols and one that exploded in an open market. At least 10 people were killed in the city Saturday.

The attack on the airport road was the most serious in months. Attacks had decreased since last year because of increased security along the six-mile stretch of highway leading from central Baghdad to the airport -- often considered the most dangerous road in the world.

The weekend also saw attacks on a string of small Shiite Muslim shrines east of Baqouba, capital of the religiously mixed Diyala province 35 miles northeast of Baghdad that has been a flash point of sectarian violence.

"These shrines are not only visited by Shiite Muslims, because they are not only Shiite imams but they are imams for all Muslims," Diyala Gov. Raid Rashid al-Mula Jawad said.

He said the shrines, often the size of a room or smaller, had "no protection because they are simple ones that some people use as graveyards."

The attacks were the latest in a surge of sectarian violence that erupted with the Feb. 22 bombing of a revered Shiite shrine in Samarra, an escalation that has worsened security and led to fears of civil war between Sunnis and Shiites.

"Such acts anger God and hurt the feeling of all honest Iraqis," Shiite cleric Adnan al-Rubaie said in Baqouba on Sunday. "The goal is clear -- to ignite civil strife. God's curse on everybody who tries to create sedition in this country."

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Associated Press writers Qassim Abdul-Zahra, Tarek El-Tablawy and Bushra Juhi contributed to this report.