BAGHDAD, Iraq - Iraq's prime minister has told Shiite militiamen to surrender their arms or face an all-out assault by US-backed Iraqi forces, senior Iraqi officials said Wednesday, as President Bush said he will commit an additional 21,500 American combat troops to the war.

People check debris after a parked car bomb also exploded in the center of Kirkuk, 290 kilometers (180 miles) north of Baghdad, Iraq, Wednesday Jan. 10, 2007. There was no immediate report on casualties. [AP]

Under pressure from the US, Prime Minister Nouri al-Maliki has agreed to crack down on fighters controlled by his most powerful political ally, Muqtada al-Sadr, a radical Shiite cleric, according to officials. Previously, al-Maliki had resisted the move.

"Prime Minister al-Maliki has told everyone that there will be no escape from attack," said a senior Shiite legislator and close al-Maliki adviser, who spoke on condition of anonymity because he wasn't authorized to speak for the prime minister. "The government has told the Sadrists: 'If we want to build a state we have no other choice but to attack armed groups.'"

In his address to the nation Wednesday evening - exerpts of which were released in advance by the White House - the president said al-Maliki had promised that USforces would have a free hand and that "political or sectarian interference will not be tolerated."

He also warned that the US expected the Iraqi leader 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 UStroops.

In the past, the Iraqi government has tried to prevent American military operations against the Mahdi Army, while giving USforces 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 UStroops 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 USforces 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 UStroops have battled Sunni insurgents along Haifa Street in central Baghdad in two major battles.

The neighborhood is only about 2 1/2 miles north of the Green Zone, site of the Iraqi government headquarters, the USEmbassy 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 UStroops, fighter jets and attack helicopters.

According to the excerpts of the president's speech released in advance by the White House, Bush will send 21,500 more troops - 17,500 of them to help pacify Baghdad,

The increase in troop levels was expected to be part of a larger military and economic effort intended to turn around a 3 1/2-year-old war that has cost the UShundreds 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-Qaida 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, USand Iraqi troops will sweep Baghdad neighborhoods in an effort to dislodge the Mahdi Army, as well as Sunni extremists - including al-Qaida in Iraq and two of its allied groups, the Ansar al-Sunnah Army and the Omar Brigade.

Iraqi and USofficials 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 USforces 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 USsoldiers 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 USofficial said al-Maliki agreed to stop protecting the Mahdi Army under pressure from both the USand his fellow Iraqis.

"It is time to perform, and that's the message he's getting from his own people, that's the message he's getting from the president and that's the message he's getting from the American people," the official said in a conference call with USreporters.

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 USand 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 USforces 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 west of the Shiite holy city of Karbala.

Police said 60 bodies, many of them victims of torture, were found in Baghdad 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 USmilitary 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.