The new Iraqi government and U.S. occupation authorities declared all militias illegal Monday and outlined a $200 million program to redirect their estimated 100,000 fighters into official security forces, retirement or civilian professions.

According to senior occupation officials, the most immediate effect of the order, issued in the name of Prime Minister Ayad Allawi, was to formally outlaw the Mahdi Army of Moqtada Sadr, the defiant Shiite Muslim cleric who has confronted U.S. occupation forces in bloody clashes for the last two months.

The order also stipulated that Sadr and his lieutenants, as members of a now illegal armed group, are barred from holding public office for three years. That put a legal barrier in the path of mainstream Shiite political and religious figures who are seeking to draw Sadr and his followers away from armed resistance and into Iraq's postwar political process.

Sadr's group rejected the ban, saying Allawi's government had no authority to hand down such laws. "Ayad Allawi's agreement does not apply to the Mahdi Army," said Omar Ahmed Shaybani, a Sadr spokesman. "The Mahdi Army is not a militia. It is the Iraqis legitimately resisting the occupation. The Mahdi Army exists as long as the occupation does."

The ban was designed in part to dramatize the intention of Allawi's government, named a week ago, to increase security measures in a country shaken by car bombings and hostage-takings directed against foreigners, and robberies and kidnappings directed against ordinary Iraqis by criminals seeking to profit from the disorder. But whether the unelected interim government can enforce such an order remains doubtful given the shaky security situation at present, said Abdul-Wahab Qassab, a retired general staff officer who runs the Azzaman Center for Strategic Studies in Baghdad.

"Unless there is a strong commitment from the political parties, I don't think the outcome will be positive," he said.

Nine other Iraqi political parties and movements have pledged to abide by the ban on militias and seek promised benefits, including job training and veterans' pensions for demobilized fighters, Allawi announced. "All of these parties have accepted detailed plans, timetables and terms for the transition and reintegration of the armed groups under their authority or have already disbanded their militias," he added.

Occupation officials said the timetable calls for as many as 90,000 fighters to turn in their weapons and change status by the time Iraq holds elections next January.

The two main Kurdish groups, the Kurdistan Democratic Party and the Patriotic Union of Kurdistan, field more than 70,000 of the 102,000 Iraqis believed to carry arms in armed political groups, according to senior officials of the U.S.-run Coalition Provisional Authority who briefed reporters on condition they not be named. The other main armed group is the Badr Organization, formerly the Badr Brigades, the military wing of the Iranian-supported Supreme Council for the Islamic Revolution in Iraq, a Shiite group with as many as 15,000 fighters.

The Badr Organization several weeks ago announced it was disbanding as a militia to become a purely political movement, although the group's weapons and fighters remained ready if its leaders saw a need for them again. By signing on to the militia ban, the group has now also pledged to turn in its guns and move its members into the new Iraqi army or police corps, or into civilian jobs, according to a negotiated transition schedule, the officials said.

But the Kurdish region's two military organizations, whose fighters traditionally are called pesh merga, have a different arrangement, reflecting the semi-independence that Kurdish-populated northern Iraq has enjoyed for more than a decade. About half are expected to join the national army or police forces, U.S. officials said. Thousands of others, they explained, will be incorporated into three specialized military units -- mountain troops, counterterrorist forces and quick-reaction battalions -- under the command of the Kurdish regional government that controls northern Iraq.

Adnan Asadi, a member of the Shiite-run Dawa party, said this arrangement should last only until Iraq gets an elected government, scheduled for next January. At that time, he said, an elected national government must reassert authority over the Kurdish region and its military forces. "This is a law and should be done," he said.

But Qassab recalled the Kurds' repeated uprisings against rule from Baghdad over the last 30 years and suggested that their acceptance of central authority might not be so simple, particularly given the often ruthless suppression of their revolts by former president Saddam Hussein's army. That is one reason for their insistence on retaining local command over part of their pesh merga military, he said.

"They are very keen to keep the ability to enforce their will wherever and whenever it becomes necessary," Qassab said.

U.S. officials have said in the past that Kurdish militias must melt into the national army at some point. The occupation officials explaining the ban, who wore button-down shirts and neckties despite Baghdad's stifling heat, insisted that, contrary to appearances, the arrangement for Kurdish fighters does not mean they remain militias under another name.

The Kurdistan Democratic Party and the Patriotic Union of Kurdistan field what amount to small armies, with organization and weaponry surpassing those of Iraq's other militias, officials said. In addition, they maintained, the history and geography of the Kurdish-administered area requires special military units of the kind that will remain under Kurdish command.

But Shaybani, the spokesman for Sadr, said the exception for the Kurds shows that Allawi's government does not exercise real power and could not impose its will on them, in part because their insistence on autonomy is supported by the United States.

"The pesh merga is an independent army, with a regional government," he said. "No Iraqi government can impose anything on that army or government."

On another subject, Shaybani said a large explosion Monday in a building adjoining the Kufa Mosque was caused by an electrical short circuit. Kufa, which lies next to Najaf about 90 miles south of Baghdad, had been the main focus of clashes between Mahdi Army fighters and U.S. troops until a cease-fire took effect Friday. Sadr frequently has led Friday prayers at the city's main mosque.

The U.S. military complained that Iraqi policemen who approached the scene of the explosion were fired on by Sadr's militiamen. Residents said the explosion came from Mahdi Army ammunition stored in the building. But Shaybani said flammable construction material was involved.

[A car bomb exploded Tuesday during morning rush hour outside a U.S. base north of Baghdad, killing four Iraqis and wounding 12 others, Iraqi police said. The explosion occurred 10 yards from the main gate of the Army's 1st Infantry Division base in Baqubah, 30 miles northeast of Baghdad.]

Special correspondent Saad Sarhan in Najaf contributed to this report.

Supporters of Sadr, who rejects the order banning his militia, chanted his praise Friday in Baghdad's Sadr City. Ruqayah Jabber Abbas wears a photo of Moqtada Sadr, a Shiite cleric now barred from office.