Iraq's political crisis worsened as five more ministers said they would boycott Cabinet meetings -- leaving the embattled prime minister's unity government with no members affiliated with Sunni factions.
Also on Monday, a suicide bomber killed at least 28 people in a northern city, including 19 children, some playing hopscotch and marbles in front of their homes. The US military also reported five new US deaths, including four soldiers who were killed in a combat explosion in restive Diyala Province north of the capital on Monday and a soldier killed during fighting in eastern Baghdad on Sunday.
The new cracks in Iraqi Prime Minister Nouri al-Maliki's government appeared even as US military officials sounded cautious notes of progress on security, citing strides against insurgents with al-Qaeda links but also new threats from Iranian-backed Shiite militias.
Despite the new US accusations of Iranian meddling, the US and Iranian ambassadors met on Monday for their third round of talks in just over two months.
A US embassy spokesman called the talks between US Ambassador Ryan Crocker and his counterpart, Hassan Kazemi Qomi, "frank and serious."
But it was al-Maliki's troubles that seized the most attention.
The Cabinet boycott of five ministers loyal to former Iraqi leader Ayad Allawi left the government, at least temporarily, without participants who 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 has a Sunni background, but has no political ties and was chosen by al-Maliki.
The Allawi 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.
Iraqi President Jalal Talabani, who has been trying to broker the Sunni bloc's return in a bid to hold the government together, met on Monday with Crocker and a White House envoy.
In Washington, US State Department spokesman Sean McCormack said the US was working well with the al-Maliki government, but he did not give the kind of enthusiastic endorsement that President George W. 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.
The ministers intend to continue overseeing their ministries.
"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.
Iraqi Brigadier General Qassim al-Moussawi, a military spokesman for Baghdad, said the government was considering a driving ban during the march this week, but had not made a decision.