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 disband his Mahdi Army or face a ban from Iraqi 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 Madhi 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.

Gun battles 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.

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 Wednesday’s planned appearance before Congress 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.

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.