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Iraq's prime minister has told Shiite militiamen to surrender their weapons or face an all-out assault, part of a commitment U.S. President George W. Bush outlined to bring violence under control with a more aggressive Iraqi Army and 21,500 additional American troops.

Senior Iraqi officials said Wednesday that Prime Minister Nouri al-Maliki, under pressure from the U.S., has agreed to crack down on the fighters even though they are loyal to his most powerful political ally, the radical Shiite cleric Muqtada al-Sadr. Previously, al-Maliki had resisted the move.

Bush laid out his new plan to quell violence in and around the Iraqi capital in a televised address to the nation Wednesday night. In earlier operations, the president said, "political and sectarian interference prevented Iraqi and American forces from going into neighborhoods that are home to those fueling the sectarian violence.

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"This time, Iraqi and American forces will have a green light to enter those neighborhoods," Bush said. "Prime Minister Maliki has pledged that political or sectarian interference will not be tolerated."

Before Bush spoke, a senior Shiite legislator and close al-Maliki adviser said the prime minister had warned that no militias would be spared in the crackdown.

"The government has told the Sadrists: 'If we want to build a state we have no other choice but to attack armed groups,"' said the legislator, who spoke on condition of anonymity because he was not authorized to speak for the prime minister.

Bush warned that the U.S. expected al-Maliki to keep those promises.

"America's commitment is not open-ended," Bush said. "If the Iraqi government does not follow through on its promises, it will lose the support of the American people and it will lose the support of the Iraqi people."

Al-Maliki on Saturday announced that his government would implement a new security plan for Baghdad, which consists of neighborhood-by-neighborhood sweeps by Iraqi forces backed by U.S. troops.

In the past, the Iraqi government has tried to prevent American military operations against the Mahdi Army, while giving U.S. forces a free hand against Sunni militants. The Bush administration has pushed al-Maliki, who took office in May, to curb his militia allies or allow U.S. troops to do the job.

Although al-Maliki withdrew political protection from the Mahdi Army, there was no guarantee the Shiite fighters would be easily routed from the large and growing area of Baghdad under their control.

The militia has more fighters, weapons and sophistication today than it did in 2004, when it battled U.S. forces to a standstill in two strongholds, the Shiite holy city of Najaf and Sadr City, Baghdad's sprawling Shiite slum.

Sunni militants, meanwhile, have put up fierce resistance in the five days since al-Maliki announced his new security initiative for Baghdad.

Iraqi and U.S. troops have battled Sunni insurgents along Haifa Street in central Baghdad in two major battles.

The neighborhood is only about 2 1/2 miles (4 kilometers) north of the Green Zone, site of the Iraqi government headquarters, the U.S. Embassy and base for thousands of American soldiers.

Eighty suspected insurgents were killed in the fighting — 50 of them on Tuesday alone, in an assault backed by U.S. troops, fighter jets and attack helicopters.

Bush said the U.S. will send 21,500 more troops — 17,500 of them to help pacify Baghdad,

The increase in troop levels was part of a larger military and economic effort intended to turn around a 3 1/2-year-old war that has cost the U.S. hundreds of billions of dollars and more than 3,000 lives.

In preparation for the new security plan, the Iraqi military will bring two brigades from northern Iraq, a region largely populated by Kurds, and one from the south.

Tens of thousands of Iraqis have died, many of them in the capital in the past year — after the war became a religious conflict between Sunnis and Shiites. Sectarian violence began after the February bombing of a major Shiite shrine by Al Qaeda in Iraq.

Al-Maliki has not commented on the Bush administration's plans to create a set of benchmarks to measure the Iraqi government's progress on improving security.

Washington wants the prime minister to come up with a plan to equitably share the country's oil wealth, ease restrictions on former Baath Party members and hold provincial elections — steps regarded as critically important to drawing Sunnis into the political process.

An Iraqi general, who spoke on condition of anonymity because he was not authorized to disclose details of the plan, said a mainly Kurdish force would be sent into the Sadr City slum in northeast Baghdad, which serves as headquarters of the Mahdi Army.

The general said Kurds, who are Sunni but not Arab, were being used against the Shiite militia because soldiers from other Iraqi units were likely to refuse to fight fellow Shiites. An estimated 80 percent of Iraq's army is Shiite.

Under the new security plan, the general said, U.S. and Iraqi troops will sweep Baghdad neighborhoods in an effort to dislodge the Mahdi Army, as well as Sunni extremists — including Al Qaeda in Iraq and two of its allied groups, the Ansar al-Sunnah Army and the Omar Brigade.

Iraqi and U.S. officials said Iraqi commanders will be put in charge of each of nine city districts. Each commander will operate independently of Iraqi military headquarters.

Al-Maliki has named Lt. Gen. Aboud Gambar, an Iraqi general who was taken prisoner of war by U.S. forces during the 1991 Gulf war, as the overall commander.

Gambar, a Shiite, will have two assistants, one from the police and one from the army, Iraqi military officers said on condition of anonymity because they were not authorized to disclose the information. Gambar will report directly to al-Maliki.

The Americans plan to put 400 to 600 U.S. soldiers in each district as a backup force, a senior Bush administration official said Wednesday. Others will be held in reserve throughout the capital to deploy quickly on the request of Iraqi commanders.

One senior U.S. official said al-Maliki agreed to stop protecting the Mahdi Army under pressure from both the U.S. and his fellow Iraqis. In a conference call with U.S. reporters, the official said the al-Maliki "plan will work" because it frees his military from political and sectarian influence.

The latest drive to pacify Baghdad is at least the fourth since the war began. All have had only limited success, with insurgents and militants swiftly returning to neighborhoods after U.S. and Iraqi military forces departed.

In the most recent of these operations, Iraq's army fielded fewer troops than promised. That made it impossible to maintain control of areas that U.S. forces had cleared of gunmen.

Police on Wednesday reported that at least 92 people had died violently or been found dead across the country.

In a single deadly attack, Sunni gunmen opened fire on a convoy of buses carrying Shiite Muslim pilgrims home from the hajj, the annual pilgrimage to Muslim holy places in Saudi Arabia, according to police and Akeel al-Khazaali, the governor of the southern province of Karbala.

At least 11 people were killed and 14 wounded. Al-Khazaali told Iraqi state television that some of the slain pilgrims had been severely burned in the ambush, which occurred about 75 miles (120.7 kilometers) west of the Shiite holy city of Karbala.

Police said 60 bodies, many of them victims of torture, were found in Baghdad on Wednesday. Seven more were discovered in the northern city of Mosul. Shootings, mortar attacks and bombings at various places around Iraq claimed another 14 lives.

The U.S. military announced Wednesday that four more American soldiers died of combat wounds in Iraq. A Task Force Lightning soldier assigned to 3rd Brigade Combat Team, 1st Cavalry Division died Tuesday from a gunshot wound sustained in the Diyala province northeast of Baghdad.

Two more soldiers died the same day in Iraq's western Anbar province. One was assigned to the 1st Marine Expeditionary Force Headquarters Group, and one was assigned to 1st Brigade, 1st Armored Division.

A 13th Sustainment Command (Expeditionary) Soldier was killed by a roadside bomb outside of Fallujah.