A U.S. soldier of the Alpha 2-17 Field Artillery 2nd Platoon is seen through a night vision device as he aims his rifle on top of a roof before a night raid in a mainly Shi'ite area in southern Baghdad March 18, 2007. [Reuters]

BAGHDAD - Sunni insurgents, resilient despite the five-week security crackdown in the capital, killed at least six more US troops over the weekend. A Sunni car bomber hit a largely Shiite district in the capital Sunday, killing at least eight people.

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The American military said four US soldiers died and one was wounded when the unit was struck by a roadside bomb in western Baghdad. During the ongoing security sweep in the capital and surrounding regions, the battalion had found eight weapons caches and two roadside bombs and helped rescue a kidnap victim, the military said.

A fifth soldier was killed in an explosion in Diyala, an increasingly volatile province just northeast of the capital. A Marine died in fighting the same day in Anbar province, the vast, largely desert region that sprawls west of Baghdad to the Saudi Arabian, Jordanian and Syrian borders. The regions are controlled by the Sunni insurgency.

All of the US victims were killed on Saturday, the military said in a series of statements that also reported that a seventh soldier died from non-combat injuries but gave no other details. While US and Iraqi troops have flooded the Baghdad streets and a heavily armored American column was sent north to adjacent Diyala province, attacks on American and Iraqi forces have been robust.

Defense Secretary Robert Gates said the success of the mission, which was starting well, could not be measured for months and that it was designed to give the Iraqis more time to settle political and sectarian differences.

"The issue that we're all trying to figure out is how best do you get the Iraqis to reconcile their differences -- because after all, this is not going to be solved by the military. It has to involve political reconciliation in Iraq, among Iraqis," Gates said on CBS's "Face the Nation."

"We're basically buying them time," he said.

The latest deaths raised the American military death toll in Iraq to 3,217 since the war began in March 2003, according to an Associated Press count.

In Shiite-controlled eastern Baghdad, a US Bradley fighting vehicle was hit by a roadside bomb Saturday evening, set afire and destroyed, said spokesman Maj. Steven F. Lamb said. There were no casualties.

Across Iraq, at least 20 people died Sunday, a sign that violence continued to abate as US and Iraqi forces press ahead with what many view as a last-chance bid to quell the sectarian violence in Baghdad and central regions of the country.

At least 12 of those killed died in Baghdad and eight of them were slain in the car bombing in a predominantly Shiite district, police said. The attack targeted people grilling meat along the street to offer as charity on a Shiite Muslim holiday marking the death of the Prophet Muhammad. Police said 28 people were wounded.

Police said the bodies of 16 people, most shot in the head and showing signs of torture, were found dumped nationwide, just five of them in Baghdad.

A US official, meanwhile, blamed al-Qaida in Iraq for chlorine bomb attacks that struck villagers in Anbar province earlier this week but said tight Iraqi security measures prevented a higher number of casualties.

Three suicide bombers driving trucks rigged with tanks of toxic chlorine gas struck targets in the insurgent stronghold including the office of a Sunni tribal leader opposed to al-Qaida. The attacks killed at least two people and sickened 350 Iraqi civilians and six US troops, the US military said Saturday.

US military spokesman Rear Adm. Mark Fox said at least one of the attackers detonated his explosives after he was blocked by an Iraqi police checkpoint in Amiriyah, just south of Fallujah, killing only himself. Fox conceded that many Iraqis were exposed to the chemical fumes but insisted that steps Iraqi security forces were increasingly effective.

"Insurgent attempts to create high-profile carnage are being stopped at checkpoints across the country," he said.

Iraqi government spokesman Ali al-Dabbagh appealed to Iraqis in the bid to curb violence.

"Opportunity is still available to all honest Iraqis to rescue this country from the criminals," he said at a joint news conference with Fox. "The chlorine attack was a kind of punishment against the people who stood against terrorist organizations."

American forces are seeing some progress in their bid to drive a wedge between insurgents in Anbar province and more mainstream Sunnis who oppose them. The insurgent chlorine bombings were viewed as part of the building power struggle between those factions.

A US Senate delegation let by John Sununu, R-N.H., met Iraq's parliament speaker in Baghdad.

"The most important challenge Iraq faces right now is security," parliament speaker Mahmoud al-Mashhadani said in a statement afterward, "and all Iraqis need to come together with support from the international community to achieve stability and impose law."