BAGHDAD — Hundreds of people fled fighting in Baghdad's Shiite militia stronghold Monday as U.S. and Iraqi forces increased pressure on anti-American cleric Muqtada al-Sadr, who faces an ultimatum to either disband his Mahdi Army or give up politics.

Al-Sadr's aides said he would only dismantle the powerful militia if ordered by top Shiite clerics _ who have remained silent throughout the increasingly dangerous showdown.

Although al-Sadr holds considerable influence through the Mahdi fighters _ estimated at up to 60,000 _ political exile for his movement would shatter his dream of becoming the major power broker among the country's Shiite majority.

Gunbattles raged around the sprawling Sadr City district that serves as the Baghdad nerve center of the Mahdi militia, which has been under siege since last week by about 1,000 U.S. and Iraqi troops.

Gunfire and explosions could be heard before dawn in Baghdad, apparently coming from the Shiite militia stronghold of Sadr City. A low-flying jet could also be heard circling the center of the capital several hours before sunrise.

Police said at least 14 civilians were killed in clashes Monday in the Baghdad area, nine of them in Sadr City. Frightened families poured out of Sadr City _ some carrying their belongings in sacks or piled in pushcarts.

Three American soldiers were killed Monday in separate attacks in the capital _ one by small arms fire and two others by a rocket-propelled grenade, the U.S. said without specifying the neighborhood or whether Shiite extremists were responsible. At least 10 U.S. soldiers have died in Iraq since Sunday.

The rapid tumble back to street battles in Baghdad _ at an intensity not seen since last year's flood of U.S. troops into the city _ is a worrisome backdrop to a planned appearance before Congress starting Tuesday by top commander Gen. David Petraeus and Ambassador Ryan Crocker to report on progress in Iraq and prospects for further troop reductions.

With the crisis showing no sign of abating, Prime Minister Nouri al-Maliki raised the stakes.

The Shiite prime minister told CNN on Sunday that al-Sadr and his followers would not be allowed to participate in politics or run in provincial elections this fall "unless they end the Mahdi Army."

Al-Maliki's statement followed a weekend declaration by top Shiite, Sunni and Kurdish leaders to support legislation banning any party that maintained a militia.

Facing broad political opposition, key al-Sadr aides went on the defensive Monday, insisting that banning them from politics would be unconstitutional. They proposed talks to resolve the standoff.

"We are calling for dialogue as a way to solve problems among Iraqi groups," al-Sadr aide Salah al-Obeidi told AP Television News in the holy city of Najaf. "Al-Sadr's office affirms that the door is open to reach an understanding regarding these problems."

Another al-Sadr aide, Hassan al-Zarqani, told The Associated Press by telephone from Iran that the Sadrists would consult Grand Ayatollah Ali al-Sistani and other top Shiite clerics in Iraq. If they "recommend he disband the Mahdi Army, he will obey," al-Zarqani said.

But it was unclear whether the statement signaled any significant change in strategy by Sadrist movement. Al-Sadr has maintained for years that only the sect's top clergy could disband the Mahdi militia.

Equally unclear was whether al-Sistani and other top clerics would take a public position on the showdown or leave it to the politicians to resolve. The aged, Iranian-born al-Sistani has remained silent since the latest crisis erupted.

Shiite clerics intervened to resolve the two uprisings against the U.S.-led coalition that al-Sadr led in 2004. Those agreements allowed al-Sadr to build his followers into a formidable political movement.

But al-Sadr, who is believed to be in Iran, has never faced such intense pressure from a broad political spectrum. His 30 seats in the 275-member parliament would not be enough to block legislation banning his movement from politics.

Al-Sadr could score significant gains in the Shiite south if his movement competes in the fall elections. That would shore up his position even without the Mahdi Army, which has tarnished his image among many Shiites because of its role in sectarian violence and crime.

Al-Sadr has called for a mass rally in Baghdad on Wednesday _ the fifth anniversary of the U.S. capture of the city _ to demand an end to the American military presence.

In Washington, White House deputy press secretary Tony Fratto called the planned demonstration "interesting timing" as it coincided with the Petraeus and Crocker testimony on Capitol Hill.

During a press conference Monday, senior Sadrist legislator Bahaa al-Aaraji called for an end to military operations around Sadr City and urged all political parties to help create an "atmosphere of calm" to "end this crisis."

Al-Aaraji also cited an Iraqi government report last year that identified 28 militias _ some believed linked to al-Sadr's Shiite rivals in the government.

"All these militias have infiltrated the government security and military institutions," al-Aaraji said. "The government has to restructure the security institutions, especially the Interior and Defense ministries, and to lift the cover of legitimacy enjoyed by some militias."

That referred to long-standing allegations that militias from al-Maliki's Dawa party and its allies, the Supreme Islamic Iraqi Council, were simply absorbed into the army and police but maintain clandestine links to their former political sponsors.

"The disbanding of militias is not meant to apply to just one party or one group," al-Maliki adviser Sadiq al-Rikabi told the AP. "Every political party that wants to contest the next election must disband and disarm its militia."

Hundreds of people fled Sadr City on Monday, trudging past U.S. and Iraqi checkpoints which prevent vehicles moving in and out of the district.

"The situation is getting very tense, said Abu Haider, 50, who left his home with a dozen family members. "News reports are not encouraging and battles are ongoing. It reminds me of when the war started and we had to leave our home. Regrettably, history is repeating itself."

The crisis erupted March 25 when al-Maliki launched a crackdown against Shiite militias and so-called "criminal gangs" in Basra. U.S. and Iraqi officials insisted the crackdown was not aimed at al-Sadr's followers but against criminals and Iranian-backed splinter groups.

However, Mahdi militiamen and other Shiite fighters responded with a wave of attacks across the Shiite south and Baghdad, where extremists pounded the U.S.-controlled Green Zone with rockets and mortars.

Violence eased March 30 when al-Sadr called on his followers to stop fighting under a deal brokered in Iran. But clashes have continued in Mahdi strongholds in Baghdad as al-Maliki insisted that the crackdown would continue until the government prevails.

"They were making allies with other groups against the government," al-Maliki aide Sami al-Askari said of the Sadrists. "In parliament, they opposed the government. But in the south, their opposition came with weapons."

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Associated Press writers Sameer N. Yacoub and Qassim Abdul-Zahra contributed to this report.