Two of Iraq's most powerful Shiite leaders agreed Saturday to end a bitter rivalry that has led to armed clashes in Baghdad and across the oil-rich south.

Radical Shiite cleric Muqtada al-Sadr and Abdul-Aziz al-Hakim, leader of the largest Shiite political party, the Supreme Islamic Iraqi Council, have promised to "protect Iraqi blood and enhance cooperation between the two movements for the Islamic and national interests and to save the nation."

The agreement comes as mainstream politicians from Iraq's majority sect have been trying to bring al-Sadr back into the fold after his loyalists pulled out of the main Shiite bloc last month.

The Sadrists' pullout left the United Iraqi Alliance, which includes SIIC, Prime Minister Nouri al-Maliki's Dawa party and some independents, with only 85 seats — a dramatic drop for an alliance that once held 130 seats in the 275-member parliament.

The deal also is an apparent bid to stem factional rivalries and violence that have threatened to spiral out of control, particularly in the oil-rich and mainly Shiite south.

The text of the agreement, signed by both leaders, was broadcast on the Shiite Al-Forat television station, which is run by SIIC. Officials representing both men confirmed the agreement but declined to give more details pending an official announcement.

The principles outlined included "the necessity of protecting and respecting Iraqi blood regardless of the situation or sect," mobilizing all Islamic and cultural institutions on both sides "to maintain friendly feelings and to avoid hatred" and to establish provincial committees aimed at keeping order.

Internal rivalries have been rising in recent months, with the assassination of two provincial governors belonging to SIIC and clashes in several cities between the Mahdi Army and Badr militiamen.

The tensions boiled over in late August when deadly street battles broke out in the holy city of Karbala during a major Shiite religious festival. Dozen of people were killed and anger mounted against the militia fighters, whom many see as criminals.

Trying to do damage control shortly after the Karbala clashes, al-Sadr announced a "freeze" of his militia activities for up to six months to allow for its restructuring. However, it is unclear how much control the youthful cleric maintains over his fighters as groups have splintered from the main movement.

The U.S. military has welcomed al-Sadr's call for his fighters to stand down but says it will continue targeting so-called rogue elements it believes are being trained and funded by Iran.

In the latest arrested, U.S. and Iraqi troops captured a suspected Shiite militia leader accused of forcibly removing Sunnis from their homes north of Baghdad was captured in a raid Friday in Khalis, a Shiite enclave in the volatile Diyala province some 50 miles north of Baghdad.

The commander was detained Friday after U.S. forces raided Khalis, a Shiite enclave of 150,000 people in the volatile Diyala province some 50 miles north of Baghdad. The man led a group of 20 insurgents that was allegedly responsible for a July attack in which Sunnis were forcibly removed and their homes and farms were destroyed, the military said, adding no one was killed or wounded.

The commander, who was not identified, also was suspected of ambushing a Sunni van driver, shooting him and throwing his body in the Tigris River, the military said.

Another pre-dawn raid Friday in the same town killed at least 25 people after troops met a fierce barrage while hunting suspected arms smuggling links between Iran and Shiite militiamen. The military described those killed in airstrikes as fighters, but village leaders said the victims included children and men protecting their homes.

The military reiterated Saturday that the 25 killed were insurgents, not civilians.

"We have confirmed that the 25 criminals who were killed were responsible for the attack on our forces and in fact were members of an extremist group operating in the Baqoubah region," the military said in a statement.

Also Friday, the U.S. military said it was investigating the deaths of three civilians shot by American sentries near an Iraqi-manned checkpoint near Musayyib, 40 miles south of Baghdad. Iraqi officials said the victims were U.S.-allied guards and were mistakenly targeted. And on Saturday, the decapitated bodies of two members of an awakening council in Iskandariyah, south of Baghdad, were found. Both were Sunnis.

While details could not be independently confirmed, the reports reflected rising concerns about possible friendly fire killings and the targeting of those who join vigilante-style groups to fight extremists and fill the vacuum left by Iraq's collapsing national police force.

Such claims could hinder crucial U.S. efforts to draw Sunni and Shiite leaders into alliances against insurgent factions such as al-Qaida in Iraq.

In other violence Saturday, a U.S. soldier was killed and three others were wounded by a roadside bombing while they were taking part in a raid against suspected insurgents in the capital, the U.S. military said in a statement.

The military also said Iraqi police had detained a fellow officer believed responsible for Thursday's killing the top district official, Abbas Hassan Hamza, and four of his bodyguards in Iskandariyah, 30 miles south of Baghdad. The suspect was accused of telling Shiite militia fighters when to detonate the explosively formed penetrator, or EFP, a weapon that the military says is being supplied by Iran.

In Poland, meanwhile, a doctor said the country's ambassador to Iraq was being kept in an artificial coma after suffering severe burns in an apparent assassination attempt earlier this week in downtown Baghdad.

The ambassador, Gen. Edward Pietrzyk, was wounded when his convoy was ambushed with roadside bombs while traveling Wednesday through downtown Baghdad. A Polish security guard and two others were killed.

Officials had initially said that Pietrzyk only suffered minor injuries, but a doctor treating him in Poland, where he was brought for treatment, described his condition as serious but stable.