Updated

Iraq's most powerful Shiite militia leader is turning to his commanders who distinguished themselves fighting U.S. troops in 2004 to screen fighters, weed out criminals and assume key positions in an effort to build a more disciplined force, two of his key lieutenants say.

That suggests the goal of Muqtada al-Sadr's temporary freeze of Mahdi Army activities, announced Aug. 29 following deadly Shiite-Shiite clashes in Karbala, is to bolster the militia to intimidate his Shiite rivals as the anti-American cleric pursues his political ambitions.

A stronger and more efficient Mahdi Army could embolden al-Sadr to take on the rival Badr militia, a move that could fragment and weaken the country's majority Shiites as gunmen battle for control of Shiite towns and cities.

Thousands of young, impoverished Shiites flocked to al-Sadr's standard after he founded the Mahdi Army a few months after the collapse of Saddam Hussein's regime in 2003.

But bands of young gunmen used the Mahdi Army's name as a cover for extortion, black marketeering and other crimes.

The task of weeding out militiamen with suspect loyalty and screening new recruits already has begun and will take months to complete, according to the two al-Sadr lieutenants, who also are militia leaders who fought the Americans in Najaf in the summer of 2004 and in Sadr City in the fall.

They spoke to The Associated Press on condition of anonymity because they are not authorized to share the information with the media and for fear of reprisals.

"The (Mahdi) army will be stronger and better organized," said one of them.

Both said the screening and reorganization process will be supervised nationwide by a 12-man council hand-picked by al-Sadr.

Under the new procedures, militiamen serving now in the ranks as well as new applicants must prove they have no criminal record, never worked for security agencies under Saddam and must submit written statements from three known community members vouching for their good character.

"Those who are found to be not telling the truth about their past will be expelled and maybe punished too," the other militia leader said. "Senior commanders who deliberately or unwittingly allow such individuals to slip through and join or retain their place in the militia will be punished too."

If the reorganization goes according to plan, the new Mahdi Army should emerge as a more disciplined and organized force — similar to its main Shiite rival, the Badr Organization, which is linked to the biggest Shiite party, the Supreme Islamic Iraqi Council.

Tension between Mahdi and Badr has been steadily rising and a showdown between them is widely expected for domination of the Shiite south, which includes most of the oil wealth and major religious shrines. Control of the shrines brings millions of dollars in donations from Shiites worldwide.

Al-Sadr is not likely to risk a head-on confrontation with the U.S. military as in 2004. But a stronger Mahdi Army would enable him to resist Washington's repeated calls to disband the militias, blamed for the wave of sectarian bloodshed that escalated last year.

A Mahdi Army firmly under al-Sadr's control could reduce what the U.S. military says are attacks by rogue Shiite militiamen controlled by Iran.

Last June, those rogue militiamen accounted for nearly 75 percent of the attacks against U.S. troops in the Baghdad area that caused casualties.

Both the government of Shiite Prime Minister Nouri al-Maliki, a one-time close ally of al-Sadr, and the U.S. military welcomed the decision to take the Mahdi Army out of action.

However, there are worrying signs that the freeze is only a cover to buy al-Sadr time to overhaul the militia, improving its mobility and combat readiness.

Al-Sadr's supporters in Basra, Iraq's second largest city, did not sign a "charter of honor" reached by representatives of 30 groups and militias there to keep the peace after British troops completed their withdrawal from the city last week.

Residents say the Mahdi Army says it is now entitled to Basra, arguing that it was its almost nightly shelling of British bases in the city and other attacks that forced them to leave. Al-Sadr's representatives in Basra have also warned they would fight U.S. troops if they move into Basra in the case of a security vacuum.

"They say they fought the British, so Basra is theirs," said Dagher al-Moussawi, a Shiite lawmaker.

In Sadr City, armed Mahdi Army militiamen stayed off the streets soon after al-Sadr made his Aug. 29 announcement but several were seen in the district over the weekend with some carrying what appeared to be U.S.-made M-4 assault rifles, the type used by American troops.

There have been reports in the United States that some of the weapons destined for Iraq's security forces have disappeared and remain unaccounted for.

Another Shiite lawmaker, who demanded anonymity for fear of reprisals, said the freeze was designed in part to spare the militia the ongoing campaign by U.S. forces and their Iraqi allies against militiamen suspected of involvement in attacks or sectarian violence.

"He wants to save the Mahdi Army by taking it out and use the time to improve it," he said.

Lt. Gen. Raymond Odierno, the No. 2 U.S. commander in Iraq, told reporters last week that mainstream Mahdi Army fighters were observing al-Sadr's order for a freeze, while U.S. military statements continue to speak of sustained attacks by "extremist" or "criminal" militiamen.

"Our assumption is that these groups are not honoring al-Sadr's orders and thus will not be subject to the restraint we have observed for those who are responding to al-Sadr's orders," said a military statement issued Sept. 4.