BAGHDAD -- Shi'ite politicians failed yesterday to persuade Sunni Arabs and Kurds to soften their opposition to a second term for Prime Minister Ibrahim al-Jaafari, leaving the Shi'ites with little choice but to replace him if they want to break the deadlock on a new government.
But Jaafari's supporters within the Shi'ite alliance showed no sign of backing down. Representatives of the seven parties within the alliance planned to meet today to discuss the standoff, which has blocked formation of a government of national unity.
''For the alliance to make a change, it needs to have the support of five of the seven blocs within it," said Salam al-Maliki, a Jaafari supporter. ''This is impossible to secure."
Names mentioned as possible alternate nominees of the alliance include Vice President Adil Abdul-Mahdi, who lost the nomination to Jaafari by a single vote; the deputy parliament speaker, Hussain al-Shahristani, an independent; and Ali al-Adeeb and Jawad al-Maliki, members of the prime minister's party.
However, none of the alternatives was believed to have broad support among enough alliance factions to be guaranteed quick approval.
The Shi'ites, the largest bloc in parliament, are under strong pressure from the United States, Britain, and their own clerical leadership to end the standoff with the Sunnis and Kurds, whom the Shi'ites need as partners in a new government.
''Forming a unity government is critical to defeating the terrorists and securing the peace," President Bush said yesterday. ''The terrorists and insurgents thrive in a political vacuum. And the delay in forming a government is creating a vacuum that the terrorists and insurgents are working to exploit."
The US military reported the deaths of three more American troops, all of them a result of hostile action in Anbar Province, a Sunni-dominated region west of Baghdad. At least 11 Iraqis were killed yesterday, police said.
In addition, five bodies were found yesterday, four in Baghdad and one south of the capital, but it was unclear when they died, police said.
Iraq's constitution states that the largest bloc in parliament gets first crack at choosing a prime minister, subject to majority approval in the legislature. The Shi'ites, who comprise the majority in the country, won 130 of the 275 seats in December, making them the biggest faction but without enough strength to govern without partners.
Jaafari, who received the nomination for another term during a vote in February among Shi'ite lawmakers, has refused to step aside. Shi'ite leaders fear that forcing him out will fragment their alliance.
A three-member Shi'ite committee met yesterday with Sunni politicians, who insisted they would never accept Jaafari. The Sunnis urged the Shi'ites to present another candidate, said Naseer al-Ani of the Iraqi Islamic Party.
''We don't know when they will get back to us," Ani said.
Kurdish leaders delivered that same message during a meeting with the Shi'ites late Sunday.
Sunnis and Kurds blame Jaafari for the rise in sectarian tensions and for a high-handed leadership style since he assumed office last year.
The debate over Jaafari has been further complicated because of divisions within the Shi'ite alliance. His strongest support comes from radical anti-American cleric Moqtada al-Sadr, whose emergence as a key political figure has alarmed both US officials and other Shi'ite leaders.
US officials have been pressing Iraqi politicians to resolve the impasse and move quickly to form a national unity government to halt violence in the country, including suicide attacks and car bombings targeting civilians, most of them Shi'ites.
Meanwhile, American troops killed a woman they said was an insurgent in a raid near Balad, north of Baghdad. Police also reported the incident, describing the woman as a farmer's wife.