Infantry sweeps through Mosul

BAGHDAD, Iraq - The U.S. military said Wednesday that a suicide bomber likely carried out the explosion at a U.S. base near Mosul, spraying a crowded mess tent with small pellets and killing 22 people - nearly all of them Americans.

The announcement raised questions about how the attacker infiltrated the base, which is surrounded by blast walls and barbed wire and guarded by U.S. troops. However, as in many other U.S. military facilities, Iraqis do a variety of jobs at the base, including cleaning, cooking, construction and office duties.

The apparent sophistication of Tuesday's operation - the deadliest single attack on U.S. troops since the war began - indicated the attacker probably had inside knowledge of the base's layout and the soldiers' schedule. The blast came at lunchtime.

"We have had a suicide bomber apparently strap something to his body ... and go into a dining hall," Gen. Richard Myers, the chairman of the Joint Chiefs of Staff, told reporters at the Pentagon. "We know how difficult this is to prevent people bent on suicide and stopping them."

Lt. Gen. Thomas Metz, commander of the multinational force in Iraq, ordered an investigation. Troops found "no physical evidence of a rocket, mortar, or other type of indirect fire weapon," according to a statement issued early Thursday by military authorities in Baghdad.

There was little apparent sympathy for the dead Americans on Mosul's deserted streets, where hundreds of U.S. troops, backed up by armored vehicles and helicopters, blocked bridges and cordoned off Sunni Muslim areas of Iraq's third-largest city.

"I wish that 2,000 U.S. soldiers were killed," declared Jamal Mahmoud, a trade union official.

Initial reports said a rocket had ripped into the tent. Later, however, a radical Sunni Muslim group, the Ansar al-Sunnah Army, claimed responsibility, saying it was a "martyrdom operation" - generally a reference to a suicide bomber.

Military officials in Iraq said Wednesday that shrapnel from the explosion included small ball bearings, which are often used in suicide bombings but are not usually part of shrapnel from rockets or mortars.

The attack sparked renewed concerns about the ability of U.S. troops and their Iraqi allies to secure elections Jan. 30. The military said they had expected an increase in violence as insurgents attempt to derail the vote for an assembly that will draft Iraq's new constitution.

"Insurgents, who have everything to lose, are desperate to create the perception that elections are not possible," said Gen. George W. Casey, the commander of multinational forces in Iraq. "We will not allow terrorist violence to stop progress toward elections."

Mortar attacks on U.S. bases, particularly on the huge, white tents that serve as dining halls, have been frequent in Iraq for more than a year. Just last month, a mortar attack on a Mosul base killed two troops with Task Force Olympia, the main force responsible for security in northern Iraq.

Tuesday's blast wrecked the mess tent at Forward Operating Base Marez, a military camp for U.S. and Iraqi government forces just south of Mosul.

The 22 dead included 13 U.S. service members, five U.S. civilians, three Iraqi National Guard members, and one "unidentified non-U.S. person," the U.S. military command in Baghdad said Wednesday evening.

Myers said authorities don't know whether the unidentified person was the likely bomber.

Of the 69 wounded, 44 are members of the U.S. military, seven are U.S. contractors, five are civilian workers for the Defense Department, two are Iraqi civilians, 10 are contractors of other nationalities, and one is of unknown nationality and occupation, the statement said.

About 50 people - most of them injured soldiers from Mosul - arrived in Germany on Wednesday aboard an Air Force C-141 transport plane. As a light snow fell, some wounded were carried away on stretchers.

Halliburton Co. lost four American employees in the attack, the Houston-based contractor said. Sixteen other Halliburton workers, including 12 subcontractors, were injured seriously.