BAGHDAD — An assault by thousands of Iraqi soldiers and police officers to regain control of the southern port city of Basra stalled Wednesday as Shiite militiamen in the Mahdi Army fought daylong hit-and-run battles and refused to withdraw from the neighborhoods that form their base of power there.
American officials have presented the Iraqi army's attempts to secure the port city as an example of its ability to carry out a major operation against the insurgency on its own. A failure there would be a serious embarrassment for the Iraqi government and the army, as well as for American forces eager to demonstrate that the Iraqi units they have trained can fight effectively on their own.
During a briefing in Baghdad on Wednesday, a British military official said that of the nearly 30,000 Iraqi security forces involved in the assault, almost 16,000 were Basra police forces, which have long been suspected of being infiltrated by the same militias the assault was intended to root out.
The operation is a significant political test for Prime Minister Nouri al-Maliki, who traveled to Basra to oversee the beginning of the assault. It is also a gamble for both the Iraqi and American governments. The Americans distrust the renegade cleric Muqtada al-Sadr and his Mahdi Army militia, who consider the Americans occupiers.
The dominant Shiite groups in Maliki's government are political and military rivals ofSadr, and Maliki is freer now to move against him because Sadr's party is no longer a crucial part of his coalition.
But if the Mahdi Army breaks completely with the cease-fire that has helped to tamp down attacks in Iraq in the past year, there is a risk of replaying 2004, when the militia fought intense battles with American forces that destabilized the entire country and ushered in years of escalating violence. Renewed attacks, in turn, would make it more difficult to begin sending home large numbers of American troops.
Maliki issued an ultimatum on Wednesday for Shiite militias in Basra to put down their weapons within 72 hours. Yet battles continued, killing at least 40 people and wounding 200 others, hospital officials said.
The assault has also sparked continuing violence by outraged Mahdi commanders in other major cities, including Baghdad, where the sprawling slum called Sadr City forms the militia's power center in Iraq.
There is minimal U.S. presence in Basra, Iraq's second-largest city, 340 miles southeast of Baghdad.
British forces turned over Basra to the Iraqis in late December, but say they will assist the Iraqis upon request.
Meanwhile, in Baghdad several volleys of rockets slammed into the U.S.-protected Green Zone for the third day this week, and the U.S. Embassy said three Americans were seriously wounded.
•Behind the Pentagon's closed doors, U.S. military leaders told President Bush Wednesday they are worried about the Iraq war's mounting strain on troops and their families. But they indicated they would support a brief halt in pulling out troops this summer. Their concern is that U.S. forces are worn thin, compromising the Pentagon's ability to handle crises elsewhere.
• Two American soldiers were killed Wednesday in separate attacks in Baghdad, the military said, raising the overall U.S. death toll since the war started more than five years ago to at least 4,003, according to an Associated Press count.
• U.S. aircraft supporting an Iraqi offensive against Shiite Muslim militias bombed suspected militia positions south of Baghdad amid intense fighting Wednesday in parts of the Iraqi capital and in the southern port city of Basra, Iraqi police said. Spokesman Muthanna Ahmed of the Babil province police said that 60 people had been hit but that he couldn't give a breakdown of dead and wounded.