Al-Jaafari had called the meeting to discuss ways to resolve the political standoff and contain a surge of sectarian killing that pushed Iraq to the brink of civil war.

Violence claimed at least 31 more lives Thursday. Among the bloodiest attacks were the bombing of a vegetable market in a mostly Shiite section of Baghdad and an assault on an Iraqi checkpoint north of the capital.

Gunmen also attacked the car of a top Sunni Muslim political leader, killing one bodyguard and wounding five. Adnan al-Dulaimi, a leader of the Sunnis' largest parliamentary bloc, had already sped away in another vehicle after his car was stopped by a flat tire, said Yassir al-Obeidi, a spokesman for his conference of the People of Iraq party.

The talks on a new government broke down last week when Sunni parties pulled out in protest against attacks on Sunni mosques triggered by the Feb. 22 bombing of a sacred Shiite shrine in the central city of Samarra. Hundreds were killed in the sectarian fury that followed.

They included 45 Sunni preachers and mosque employees, according to Sheik Ahmed Abdul Ghafour al-Samaraie, head of the government's Sunni Endowment, which takes care of Sunni mosques and religious shrines.

He told a news conference Thursday that 37 Sunni mosques were destroyed and 86 damaged by grenade, rocket or bullet fire. Six others remained in the hands of Shiite militiamen, he said. U.S. military officials put the figures much lower.

Yet another Sunni cleric was gunned down as he left a mosque after dawn prayers Thursday in Basra, in the southern Shiite heartland. It was not clear if the cleric was included in al-Samaraie's count.

The former U.N. human rights chief for the country said abuses are as bad now as they were under Saddam Hussein. Extrajudicial killings and torture are soaring, and morgue workers are being threatened by both government-backed militiamen and insurgents not to properly investigate deaths, he said in an interview in Sydney, Australia.

"Under Saddam, if you agreed to forego your basic right to freedom of expression and thought, you were physically more or less OK," said John Pace, who last month left his post as director of the human rights office at the U.N. Assistance Mission for Iraq. "But now, no. Here, you have a primitive, chaotic situation where anybody can do anything they want to anyone."

As violence surged last week, the U.S. 2nd Brigade, 1st Armored Division was put on alert in neighboring Kuwait for a possible move into Iraq, the military said. But no such orders were given.

The sectarian killing has eased since then, but bloodshed continues.

The blast during the busy morning shopping period at a vegetable market in Baghdad's southeastern Zafaraniyah neighborhood killed at least eight people and wounded 14, said police Lt. Bilal Ali Majid. Police evacuated the market after finding a second bomb.

Another bomb ripped through a minibus driving in Sadr City, the east Baghdad Shiite ghetto, killing the driver and a passenger. Four bystanders were hurt, said police Col. Khazim Abbas.

A fourth device went off as Interior Ministry commandos drove through the Sunni-dominated Amariyah neighborhood in western Baghdad, killing one of them and injuring three, police 1st Lt. Maitham Abdul-Razaq said.

Earlier, gunmen attacked a joint police-army checkpoint about 20 miles north of Samarra, killing six soldiers and four policemen, said police Lt. Qassim Mohammed. The attackers set fire to the bodies before fleeing the area, he said.

Four more policemen were killed when gunmen intercepted their vehicle in Mosul, 225 miles northwest of Baghdad, said police Brig. Abdel Hamid al-Jbouri. And police found the bodies of four blindfolded men shot in the head in Sunni-dominated parts of western Baghdad.

The violence has complicated talks to form a broad-based government, which U.S. officials consider essential to lure Sunni Arabs away from insurgents so coalition forces can start drawing down later this year.

Al-Jaafari's office gave no reason for calling off Thursday's meeting with major political parties.

"The cancellation of this meeting is a regrettable thing because such meetings are essential under the current situation," said Mahmoud Othman, a leading figure in Parliament's Kurdish bloc.

On Wednesday, leaders of three parties, including Sunnis, Kurds and the secularists of ex-Prime Minister Ayad Allawi, agreed to ask the main Shiite bloc to withdraw al-Jaafari's nomination for prime minister and put forward another candidate. Officials of all three groups confirmed the plan but spoke on condition of anonymity because of the sensitivity of the subject.

The Shiites won 130 of Parliament's 275 seats in December elections, giving them the largest bloc of lawmakers and the first chance to form a government — but not enough to govern without partners.

Al-Jaafari won the nomination by a single vote in a Feb. 12 ballot among Shiite lawmakers, defeating Vice President Adil Abdul-Mahdi in large part due to the support of anti-U.S. cleric Muqtada al-Sadr.

The move against al-Jaafari is expected to draw sharp opposition from al-Sadr, who hasn't yet commented.

Al-Sadr's militiamen were believed behind many of the attacks against Sunni mosques last week, and the prospect of a prime minister in debt to the young radical has alarmed mainstream politicians, including some in the Shiite alliance.

Bombings, gunfire and mortar blasts killed 47 more people Wednesday.

A U.S. soldier assigned to Multinational Division-Baghdad died in a non-combat related incident Wednesday, the military said. No details were provided. At least 2,295 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count. The figure includes seven military civilians.

In court Wednesday, Saddam Hussein took sole responsibility for ordering the trial of 148 Shiites who were eventually executed in the 1980s. But he insisted this was no crime as they were suspected of participating in an assassination plot against him. The trial was then adjourned until March 12.

Associated Press writers Bassem Mroue, Sameer N. Yacoub and Steven R. Hurst contributed to this report from Baghdad.