Baghdad, Iraq ? The U.S. ambassador delivered a blunt warning to Iraqi leaders Monday that they risk losing American support unless they establish a national unity government with the police and the army out of the hands of religious parties.

Ambassador Zalmay Khalilzad delivered the warning as another 24 people, including an American soldier, died in a string of bombings, underscoring the need for the country to establish a government capable of winning the trust of all communities and ending the violence.

Such a government is also essential to the U.S. strategy for handing over security to Iraqi soldiers and police so the 138,000 U.S. troops can go home. But talks among Iraqi parties that won parliament seats in the Dec. 15 election have stalled over deep divisions among Shiites, Sunni Arabs and Kurds.

During a rare news conference, Khalilzad said division among the country’s sectarian and ethnic communities was “the fundamental problem in Iraq,” fueling the Sunni Arab-dominated insurgency and the wave of reprisal killings.

“To overcome this there is a need for a government of national unity,” which “is the difference between what exists now and the next government,” he said. The outgoing government is dominated by Shiites and Kurds.

Khalilzad said Iraq’s next Cabinet ministers, particularly those heading the Interior and Defense ministries, “have to be people who are nonsectarian, broadly acceptable and who are not tied to militias” run by political parties.

Otherwise, he warned that “Iraq faces the risk of warlordism that Afghanistan went through for a period.” Khalilzad was born in Afghanistan and served as U.S. envoy there.

To underscore his remarks, Khalilzad reminded the Iraqis that the United States has spent billions to build up Iraq’s police and army and said “we are not going to invest the resources of the American people and build forces that are run by people who are sectarian” and tied to the militias – some of which the ambassador said received “arms and training” from Iran.

British Foreign Secretary Jack Straw, who arrived in Baghdad late Monday, was expected to reinforce Khalilzad’s message during meetings with Prime Minister Ibrahim al-Jaafari and other Iraqi leaders.

Iraqis inspect the wreckage of a bus following an explosion in Baghdad, Monday, Feb. 20, 2006. A suicide bomber detonated his explosives belt on a bus Monday in the Shiite district of Kazamiyah, killing 12 people and injuring 15, police said.

There was no response from al-Jaafari’s government to Khalilzad’s warning, but a prominent Shiite politician, Jalaladin al-Saghir, said the comments were “unacceptable” and constituted interference in the affairs of a sovereign state.

“We all want a national unity government and the U.S. ambassador is no more eager than we are to reach such a government,” al-Saghir told The Associated Press. “It is the Americans who push toward sectarianism by their ever-changing points of view. We feel uneasy about some of the U.S. agenda.”

Al-Saghir said the Americans had installed former members of Saddam Hussein’s Baath party in the Interior and Defense ministries and “Shiites are upset about this.”

In Najaf, al-Jaafari said formation of the government was more complicated “because this time the Arab Sunnis are participating in the political process.”

Wave of bombings

In the latest bloodshed, an American soldier was killed Monday by a roadside bomb near Karbala, a Shiite shrine city about 50 miles southwest of Baghdad. The death brought to at least 2,274 the number of members of the U.S. military to have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

A suicide bomber detonated an explosives belt on a bus Monday in Baghdad’s Shiite district of Kazimiyah, killing 12 people and wounding 15, police said. Earlier, a bomb exploded next to tea stalls near Liberation Square in central Baghdad, killing at least four day laborers and wounding 14, police said.

In Mosul, 225 miles northwest of Baghdad, a suicide attacker blew himself up in a restaurant packed with policemen eating breakfast, killing at least five people and wounding 21, including 10 policemen, officials said.

The Shura Council for Mujahedeen in Iraq claimed responsibility in a statement posted on an Islamic Web site, saying one of the “lions of monotheism” attacked the restaurant because it was “frequented by apostate policemen.”

Two more civilians died when a car bomb exploded in Madain, southeast of Baghdad, police said. Eleven people, including three women, were wounded.