( Reuters ) - The main Sunni Arab political bloc quit the Iraqi government on Wednesday in a blow to Prime Minister Nuri al-Maliki, while a suicide bomber driving a fuel truck killed 50 people in one of several car bombs in Baghdad.
The Sunni Accordance Front announced its pull-out from Maliki's Shi'ite-led coalition over his failure to meet a list of about a dozen demands, including a greater say in security matters.
The front's 44 members will remain in the 275-seat parliament. Its withdrawal will have little practical effect on the 15-month-old government, which is virtually paralyzed by infighting but needs only a simple majority to keep functioning.
But the shaky coalition is under pressure from the United States and its allies to end sectarian strife between Shi'ites and Sunnis through national reconciliation.
Washington is unhappy at the slow progress towards political benchmarks meant to draw minority Sunni Arabs, dominant under Saddam Hussein, into the political process and away from an insurgency that has killed tens of thousands.
Police said the suicide bomber was driving a fuel truck packed with explosives in the attack in Mansour district of western Baghdad that wounded 60 people apart from the 50 killed.
They said the bomber lured motorists queuing for petrol to his truck after earlier saying he had rammed into the line of vehicles.
Separately, 20 people were killed and 40 wounded when a suicide bomber blew up his vehicle near a popular ice cream parlor in a bustling area full of electronics stores in Baghdad's predominantly Shi'ite district of Karrada.
In southern Baghdad, a parked car bomb killed three people and wounded five in Doura district, police said.
The U.S. military, which began a build-up of 30,000 extra troops this year in a bid to buy time for Maliki to meet his political targets, said three of its soldiers were killed by a roadside bomb in the east of the capital on Tuesday.
The Accordance Front is made up of three main Sunni groups, including Vice President Tareq al-Hashemi and the head of the bloc, Adnan al-Dulaimi. Its list of demands also included the disbanding of Shi'ite militias.
Maliki's government has already been weakened by the withdrawal of fiery Shi'ite cleric Moqtada al-Sadr's political bloc, one of the biggest in parliament, over his refusal to set a timetable for the withdrawal of U.S. troops.
The Accordance Front, which last week suspended the work of its six ministers in government and gave Maliki a week to meet its demands, had accused the Shi'ite led-coalition government of failing to consult it on key issues.
Accordance Front official Rafei Issawi said the Deputy Prime Minister Salam al-Zobaie and five ministers would present their resignations to Maliki later on Wednesday.
Iraq's other deputy prime minister, Kurd Barham Salih, said the Sunni bloc's withdrawal was the most serious political crisis Iraq had faced since the passage of Iraq's new constitution after an October 2005 referendum.
"If unresolved the implications are grave," Salih told Reuters.
Salih said preparations were continuing for a summit of the political leadership of Iraq's Kurdish, Shi'ite and Sunni Arab communities, which would take place in "the next few days."
"The crisis is grave and its implications should not be underestimated, but I hope it offers an opportunity to address the causes of political instability afflicting this country," Salih said.
Along with the oil law, the political targets include a law to ease restrictions on former members of Saddam's Baath party serving in the military and civil service, provincial polls and constitutional reform.
The deaths of the three U.S. soldiers took the total killed in July to at least 77, the lowest monthly toll for the U.S. military in Iraq since last November and the lowest since the build-up of 30,000 extra U.S. troops began in February.
The commander of U.S. forces in Iraq, General David Petraeus, and U.S. Ambassador Ryan Crocker are due to deliver a progress report to Congress in mid-September as U.S. President George W. Bush comes under pressure to show progress in the unpopular war or begin withdrawing troops.