Baghdad, Iraq ? Sunni Arab militants killed 14 Shiite militiamen and a policeman Thursday in a clash southeast of Baghdad – another sign of rising tensions among Iraq’s rival ethnic and religious communities. The U.S. military reported three more American soldiers died in combat.

The Shiite-Sunni fighting occurred after police and militiamen loyal to radical Shiite cleric Muqtada al-Sadr raided a house in Nahrawan, 15 miles southeast of the capital, to free a militiaman taken hostage by Sunni militants, according to Amer al-Husseini, an aide to al-Sadr.

After freeing the hostage and capturing two militants, the Shiite militiamen were ambushed by the Sunnis on their way out of the religiously mixed town, al-Husseini said. Police Lt. Thair Mahmoud said 14 others – 12 militiamen and two policemen – were wounded.

The incident underscores tensions among hard-line elements in Iraq’s rival religious and ethnic communities at a time when the United States is struggling to promote a political process seen as key to calming the insurgency so that U.S. and other foreign troops can go home.

Shiites and Sunnis have accused one another of kidnappings and assassinations, especially in religiously mixed Baghdad neighborhoods and farming communities south and east of the capital. Majority Shiites and minority Kurds generally support the Shiite-dominated government, while Sunni Arabs dominate the ranks of the insurgents.

Iraqi Prime Minister Ibrahim Al-Jaafari, center, reviews a Jordanian guard of honor as he arrives Thurs-day at Amman Airport, Jordan. Al-Jaafari arrived on his first trip to Jordan to boost political, security and economic cooperation.

Sectarian violence has complicated efforts by the United States and its coalition partners to promote a political process, which received a boost this week with the announcement that voters had approved the new constitution in the Oct. 15 referendum, despite strong opposition from the minority Sunni Arab community.

Ratification paves the way for parliamentary elections Dec. 15. Some Sunni groups have decided to field candidates in the election, signaling a desire to participate in politics. Most Sunnis boycotted the last parliamentary election in January.

U.S. officials hope Sunni Arab participation will draw away support for the Sunni-led insurgency and allow Washington to draw down forces in Iraq before midterm elections in November next year.

The U.S. command said two more Army soldiers were killed Wednesday when their convoy hit a roadside bomb in Baghdad. Another U.S. soldier died Wednesday in an ambush 37 miles north of Baghdad, the military said. Four other soldiers were wounded.

The deaths raised the U.S. military death toll to at least 2,004 since the start of the war in 2003, according to an Associated Press count.

U.S. Marines also killed three insurgents in fighting Thursday in Ramadi, capital of volatile Anbar province, 70 miles west of Baghdad.

With attention now focused on the December elections, Iraqi political parties are locked in intensive negotiations to put together lists of candidates, which must be submitted to the election commission by today.

Three Sunni Arab groups have announced they will field a joint candidate list, and the Shiite-dominated United Iraqi Alliance, which won 146 of the 275 seats in the January balloting, was meeting Thursday to try to put together a ticket.

Shiite politicians said the last-minute talks were an effort to convince Deputy Prime Minister Ahmad Chalabi, a former Pentagon insider, to joining the Alliance ticket. Chalabi ran under the Alliance standard in January but is apparently holding out for a promise of a greater role if the Shiites control the next government.

“I think that Dr. Chalabi will be part of the United Iraqi Alliance,” said Shiite politician Abbas al-Bayati. “He is keen to be within the alliance, and the alliance is keen to include him.”