BAGHDAD (AP) - The U.S.-led coalition said it killed 30 fighters in a battle yesterday with the country's most powerful Shiite militia amid growing American impatience with the Iraqi government's inability to stop militias responsible for escalating sectarian violence.

The clash was the second with the Mahdi Army in the predominantly Shiite southern city of Diwaniyah in as many months. Officials from the party of radical Shiite cleric Muqtada al-Sadr, which heads the militia, denied any of their fighters were killed.

A U.S. Abrams tank was seriously damaged when it was hit by rocket-propelled grenades, but no casualties were reported among the U.S. or Iraqi forces.

However, the military announced the deaths of five U.S. troops elsewhere in the country. Two soldiers were killed Saturday - one in the capital and the other northwest of Baghdad - while three Marines were killed Friday in western Anbar province, the military said without elaborating.

The deaths brought to 29 the number of Americans killed in Iraq this month - many of them in Baghdad as part of a district-by-district crackdown aimed at reducing mounting violence by clearing the city of weapons and fighters.

At least 14 Iraqis also died in other violence around the country Sunday, including a Shiite woman and her young daughter who were killed when gunmen opened fire on their minivan in Baqouba, northeast of Baghdad. The driver also was killed, and the woman's husband and her brother were wounded.

Police also found 51 bullet-riddled bodies in various parts of Baghdad during a 24-hour period ending yesterday morning, police 1st Lt. Mohammed Khayoun said. They were all apparent victims of the sectarian death squads that roam the capital, with many of the bodies showing signs of torture.

The U.S. has shown increasing impatience with the failure of Shiite Prime Minister Nouri al-Maliki to rein in militias fueling the Shiite-Sunni killings that many believe now pose a greater threat to Iraq's stability than al-Qaida or the anti-U.S. insurgency.

Sunni leaders accuse al-Maliki of hesitating to take action against Shiite militias because many of them - like the Mahdi Army - belong to political parties that his government relies on for support. Al-Sadr's party holds 30 of the 275 seats in parliament and five Cabinet posts, and the cleric's backing helped al-Maliki win the top job earlier this year.

U.S. Secretary of State Condoleezza Rice gave al-Maliki and other Iraqi leaders a blunt assessment during a visit to Iraq this past week, telling them the violence cannot be tolerated and they have to act.

Sen. John Warner (R-Va.) chairman of the Armed Services Committee, gave a starker warning following his own visit to Iraq, saying if violence does not abate in the next two or three months, Washington should make "bold decisions" on what to do next.

U.S. troops have been quietly launching raids on key al-Sadr loyalists and Mahdi Army members in the past week, members of al-Sadr's party have said. The U.S. has announced numerous arrests during the Baghdad sweep, but has not specified what group they belong to so exact numbers could not be determined.

Al-Sadr loyalists, meanwhile, have accused the Americans of trying to start a wider fight with the militia. U.S. troops and the Mahdi Army fought major battles twice in 2004.

"The Americans are creating pretexts to provoke us and drag us into confrontation," said Fadhil Qasir, a spokesman for the Mahdi Army in Diwaniyah.

The fighting in Diwaniyah, about 80 miles south of Baghdad, broke out after U.S. and Iraqi troops entered the city looking for Mahdi Army members responsible for the execution-style killings of 11 Iraqi army troops in August. The slayings provoked a fierce fight at the time between the militia and Iraqi forces that left 23 troops and 50 militiamen dead.