Khalilzad has been pressing political leaders to reach agreement on a national unity government, under which the country's majority Shiite Muslims would share Cabinet posts equitably with minority Sunnis and Kurds.

The Americans see that as the best way to blunt the Sunni-driven insurgency that has ravaged the country since 2003. If a strong central government were in place, Washington had hoped to start removing some troops by summer.

The parliamentary session comes as the U.S. military braces for violence. Monday marks the third anniversary of the U.S.-led invasion of Iraq on March 20,2003. It coincides with a major religious commemoration that came under attack in the two previous years.

The military dispatched a battalion of soldiers from the 2nd Brigade, 1st Armored Division ¡ª about 700 troops ¡ª to Iraq from its base in Kuwait to provide extra security as tens of thousands of pilgrims converged on Shiite holy cities.

Authorities in one of the cities, Karbala, imposed a six-day driving ban starting Thursday in a bid to protect pilgrims this year.

In violence Wednesday, a U.S. airstrike north of the capital killed 11 people ¡ª most of them women and children, said police and relatives of the victims. The U.S. military said it captured the target of the raid, a man suspected of supporting foreign fighters of the al-Qaida in Iraq terror network.

But the military said it could only account for four people killed ¡ª a man, two women and a child. "That doesn't meant that we dispute 11," said Maj. Tim Keefe, a military spokesman.

He said the suspect was captured as he fled the house, but U.S. troops were taking fire from the building and called in an airstrike. He did not specify whether the strike near Balad, 50 miles north of Baghdad, involved warplanes or gunships.

AP photographs showed the bodies of two men, five children and four other covered figures arriving at the hospital in nearby Tikrit, accompanied by grief-stricken relatives.