Five more ministers announced a boycott of Cabinet meetings worsening the political situation in Iraq. As a result prime minister's unity government has no members affiliated with Sunni political factions at the moment. Meantime a suicide bomber killed at least 28 people in a northern city, including 19 children, some of them playing in front of their houses.
The new cracks in Prime Minister Nouri al-Maliki's government appeared even as U.S. military officials sounded cautious notes of progress on security, citing strides against al-Qaida in Iraq-linked insurgents, but also new threats from Iranian-backed Shiite militias.
Despite the new U.S. accusations of Iranian meddling, the U.S. and Iranian ambassadors met Monday for their third round of talks in just over two months. A U.S. embassy spokesman called the talks between U.S. Ambassador Ryan Crocker and his counterpart, Hassan Kazemi Qomi, "frank and serious."
But it was al-Maliki's troubles that seized most attention.
The Cabinet boycott of five ministers loyal to former Iraqi leader Ayad Allawi left the government, at least temporarily, without participants where were members of the Sunni political apparatus - a deep blow to the prime minister's attempt to craft reconciliation among the country's majority Shiites and minority Sunnis and Kurds.
The Defense Minister is from a Sunni background but has no political ties and was chosen by al-Maliki.
The Allwawi bloc, a mixture of Sunnis and Shiites, cited al-Maliki's failure to respond to its demands for political reform. The top Sunni political bloc already had pulled its six ministers from the 40-member Cabinet of al-Maliki, a Shiite, last week.
Iraq's president, Jalal Talabani, has been trying to broker the Sunni bloc's return in a bid to hold the government together, and met Monday with Crocker and a White House envoy.
In Washington, State Department spokesman Sean McCormack said the United States was working well with the al-Maliki government, but he did not give the kind of enthusiastic endorsement that President Bush and his aides once did.
"There's a very healthy political debate that is going on in Iraq, and that is good," McCormack said. "It's going to be for them (the Iraqi people) to make the judgments about whether or not that government is performing."
Lawmaker Hussam al-Azawi of the bloc loyal to Allawi, said the boycott began with Monday's Cabinet meeting but others said the ministers would continue to do other government work.
"We demanded broader political participation by all Iraqis to achieve real national reconciliation ... and an end to sectarian favoritism," al-Azawi said.
Meanwhile, Iraqi authorities girded for a major Shiite pilgrimage later this week in Baghdad with plans to tighten security.
Sunni insurgents often target such gatherings. And this particular annual march, to commemorate the eighth-century death of a key Shiite saint, was struck by tragedy in 2005, when thousands of Shiite pilgrims, panicked by rumors of a suicide bomber, broke into a stampede on a bridge, killing 1,000.
Brig. Gen. Qassim al-Moussawi, an Iraqi military spokesman for Baghdad, said the government was considering a driving ban during the march this week, but had not made a decision.
However, Iraqi security forces will intensify checkpoints and marchers will be banned from carrying weapons, cell phones or even bags, he said.
In Tal Afar to the north, officials slapped an immediate curfew on the religiously mixed city after a suicide bomber slammed his truck into a crowded Shiite neighborhood, killing the 28.
The powerful Monday morning blast caused houses to collapse as many families were getting ready for the day ahead, and officials said the death toll could rise. Many of the casualties were women and children, officials said.
Several residents said boys and girls were playing hopscotch and marbles outside the houses at the time of the explosion.
"This is an ugly crime. I cannot understand how the insurgents did not think about these children," said one man, Kahlil Atta, a wedding photographer in the city.
The attacker drove a dump truck filled with explosives and covered with a layer of gravel, Brig. Gen. Najim Abdullah said. He said at least 19 children were among those killed.
Tal Afar, which was cited by Bush last March as a success story after major military operations against insurgents, has been the frequent site of Sunni extremist attacks in the past year.
Elsewhere, 60 decomposing bodies were found in a mainly Sunni area that had been under the control of al-Qaida in Iraq west of Baqouba, according to a Diyala police official. The U.S. military said it had no information about any discovery.
At least 53 other people were killed or found dead elsewhere in Iraq, according to police. Those included the bodies of five soldiers who had been ambushed by gunmen while on their way home for vacation north of Tikrit.
A U.S. soldier was killed and two were wounded Sunday during fighting in eastern Baghdad, the military said Monday.
The Iranian talks come as the U.S. military steps up accusations that Tehran is arming and training Shiite militants to attack American forces in Iraq.
Lt. Gen. Raymond Odierno, the U.S. second-in-command, said Sunday that rogue Shiite militiamen with Iranian weapons and training launched 73 percent of the attacks that killed or wounded American forces last month in Baghdad, nearly double the figure six months earlier.
Tehran has denied U.S. allegations that it is fueling violence in Iraq.
On Monday, the Iranian delegation criticized what it called America's "suspicious" security approach toward Iraq, according to the Islamic Republic News Agency. It called for "a change in the broad policies and approach of the U.S."