At least 21 Shiite militia fighters and two policemen were killed in clashes with Sunni insurgents near Baghdad, in a flare-up likely to fuel mistrust between Iraq's two main religious sects. The clashes came hours after Iraq's ruling Shiite Islamist parties struck a last-minute deal to patch up differences and agreed to register as a united bloc for December 15 polls where they face a new Sunni Arab alliance.

On the diplomatic front, Iraqi Prime Minister Ibrahim al-Jaafari began a landmark visit to Jordan to boost once close political and economic ties between the two neighbors.

Militiamen from Moqtada al-Sadr's Mehdi Army called for police backup as they mounted an operation to recover a comrade being held in Al-Khazaliyya, but the group was caught in an ambush, an Interior Ministry source said.

Two policemen also died in the ensuing firefight, while 12 militiamen were wounded.

The battle took place in Nahrawan, southeast of Baghdad, an area with a mixed Sunni and Shiite population where insurgents have staged major attacks on Iraqi police and U.S.-led forces.

The latest violence came as politicians in Baghdad were racing to finalize their slates by a Friday deadline to register parties and coalitions for the December parliamentary election.

Officials within the Shiite United Iraqi Alliance said it would run as a single elector-al list.

"The United Iraqi Alliance has been revived," said Jawad Maliki, the number two figure in the Daawa party, stressing that it has yet to be decided how many candidates each party within the alliance would field.

Three principle Shiite movements are involved: the powerful Supreme Council for the Islamic Revolution in Iraq (SCIRI), formed in exile in Iran to oppose Saddam Hussein and led by Abdel-Aziz al-Hakim; the Daawa party of Jaafari; and Sadr's movement.

In January's vote, the United Alliance took a majority of seats, helped by the blessing of Grand Ayatollah Ali Sistani, spiritual guide to the Shiite majority.

Aides to the reclusive cleric, however, have indicated that he will refuse to back a specific party in the December vote.

The move reflected the cleric's disappointment with the performance of Jaafari's government, according to the associates.

On Wednesday, three leading parties from the Sunni Arab minority formed a coalition to contest the election.

The two main Kurdish movements, which joined the Shiite alliance in the interim government, have also agreed to run on a joint ticket again, despite long-standing rivalries.

Members of Parliament said that among changes agreed in the Shiite deal, Sadr's movement would have a more formal role in the alliance.

"The parties signed the agreement last night, shares are already being distributed according to each party and what it will get," a source in the alliance said.

Although Sadr has three allies in the present Cabinet, he has been ambivalent in public about the government. His Mehdi Army has clashed recently across Shiite southern Iraq with the Badr militia forces of Hakim's SCIRI.

On his first trip to Jordan as prime minister, Jaafari met with King Abdullah II, who described last week's constitutional referendum as a "milestone" toward building a new Iraq.

"The support of the majority of Iraqi people to the referendum is a milestone toward building a new Iraq," Abdullah said.

Abdullah condemned all "terrorist actions which target innocent civilians and aim at undermining Iraq's security and stability," according to a statement issued by the king's office following his one-hour meeting with Jaafari.

He repeated his call on Iraq's minority Sunni Arabs to participate in their country's political development.

Jaafari, who is leading a top Iraqi delegation, was received with a red carpet at Amman's Marka Air Base and was greeted by his Jordanian counterpart, Adnan Badran.

Both premiers later chaired meetings of a joint Jordanian-Iraqi committee, which sets guidelines on bilateral cooperation like border controls, preventing dual taxation and political coordination.

Separately, Iraqi Foreign Minister Hoshyar Zebari said resolving a fraud conviction that has long hung over Ahmad Chalabi, Iraq's deputy prime minister, was not on Jaafari's agenda.

Jordanian Deputy Prime Minister Marwan al-Muasher said the kingdom would "only discuss this matter within its legal framework."

Jordan's military court convicted Chalabi in absentia in 1992 of embezzlement, fraud and breach of trust after a bank he ran collapsed with about $300 million in missing deposits. Chalabi, who denies wrongdoing, was sentenced to 22 years in prison in Jordan but has served none.