Two suspected Shiite militia leaders surrendered Friday during American raids on their homes south of Baghdad, the U.S. military said.

One of the men is suspected of ordering attacks on U.S. troops, directing the kidnapping of Iraqis and smuggling Iranian weapons and Katyusha rockets into Iraq, according to a statement from the military. The other suspect tried to flee by wading through an irrigation canal, before surrendering.

The U.S. said the men were members of Iranian-backed "special groups" — language the American military uses to describe Shiite fighters defying a cease-fire order by anti-American cleric Muqtada al-Sadr.

Some of the men are believed to have fled recent fighting in the Shiite militia stronghold of Sadr City, but others have been based for years in swaths of overwhelmingly Shiite territory south of the Iraqi capital. The area is home to several of Shiite Islam's holiest shrines.

Such arrests have become an almost daily occurrence in Iraq, where U.S. forces are seeking to thwart the movement of Iranian weapons into Iraq. Washington accuses Iran of arming and training Shiite militiamen, but Tehran denies that.

The campaign of arrests was likely to be on the agenda for talks when Iraqi Prime Minister Nouri al-Maliki travels Saturday to Tehran for his second trip there in a year.

He is expected to discuss with Iranian leaders Washington's accusations of Iranian meddling in Iraq, as well as a proposed security agreement between the U.S. and Iraq.

The deal, which the Iraqis and Americans hope to finish by midsummer, would establish a long-term security relationship between Iraq and the United States, and a parallel agreement would provide a legal basis to keep U.S. troops in Iraq after the U.N. mandate expires at the end of the year.

Supporters believe the deal would help assure Iraq's Arab neighbors, notably Saudi Arabia and the Gulf States, that Iraq's Shiite-led government would not become a satellite of Iran, the largest Shiite nation, as the American military role here fades.

But critics in Iraq worry the deal will lock in American military, economic and political domination of the country. Some Iraqi politicians have attacked the deal, especially those loyal to al-Sadr, whose militiamen fought U.S. and Iraqi troops in Sadr City for seven weeks this spring, until a truce in May.

The cleric himself is believed to be living in the Iranian city of Qom.

Al-Maliki's Dawa party has described talks over the U.S.-Iraqi security pact as stalled, with almost every provision under dispute.

The party has also sought to calm worries by insisting that the deal would not allow foreign troops to use Iraq as a ground to invade another country — a reference to Iranian fears of a U.S. attack.

The challenge for al-Maliki, himself a Shiite, is to maintain ties with Iran while at the same time ensuring his support from the United States. He needs to persuade the Iranians to rein in Shiite extremists but also assure them that security ties to the U.S. would not threaten the Islamic Republic.

Also Friday, a homicide bomber that Iraqi police said they believed was a woman exploded herself near a checkpoint in a village outside Ramadi, wounding two policemen. Police said they were searching for another woman who fled the scene and may have been a second bomber.

Ramadi is the capital of Iraq's western Anbar province, which saw heavy fighting with Al Qaeda-linked militants until Sunni Arab sheiks began partnering with U.S. forces there in 2006.

The U.S. military issued three additional statements Friday saying its soldiers killed four suspects and captured more than 57 others in raids earlier in the week in Baghdad and across northern Iraq.