Prime Minister Ibrahim al-Jaafari stood firm Wednesday, insisting he is the Shiite nominee for a new term and to step down is "out of the question." Officials called a session of parliament to try to break the political deadlock caused by disputes over his candidacy.

Efforts to form a national unity government in Iraq have been stalled for months. Sunnis and Kurds oppose al-Jaafari, blaming him for the rise in sectarian tensions across Iraq and for a high-handed leadership style since he assumed office last year.

But al-Jaafari repeatedly has said he was nominated democratically and it's up to parliament to decide whether to approve him. He insisted Wednesday that he still enjoys the support of the Shiite alliance, the dominant bloc in parliament, despite a few public calls from within for him to step aside.

"As a matter of principle, I think the idea of making a concession is, for me at least, out of the question," al-Jaafari said in a nationally televised press conference.

Shortly after, the parliament media office announced that a session would be held at 4 p.m. Thursday. Speaker Adnan Pachachi confirmed the session but began a closed-door meeting and was unavailable to give more details.

The 275-member assembly had been set to convene Monday but agreed to a delay to give Shiites time to resolve the dispute over their nomination of al-Jaafari to head the new government. U.S. and British officials urged the session go ahead and decide on other posts, including parliament speaker and the vice presidents, trying to build momentum to resolve the political deadlock.

On Wednesday, President Bush called on the Iraqis to "step up and form a unity government so that those who went to the polls to vote recognize that a government will be in place to respond to their needs."

"We understand full well that the political process in Iraq must occur soon," Bush told reporters on the White House South Lawn. "I don't expect everybody to agree with my decision to go into Iraq. But I do want the people to understand, the American people to understand, that failure in Iraq is not an option."

Iraq's constitution states that the largest bloc in parliament gets first crack at the prime ministership, subject to majority approval in the legislature. The majority Shiites won 130 seats in December, making them the biggest faction but unable to govern without partners.

The debate over al-Jaafari has been further complicated because of divisions within the Shiite alliance. His strongest support comes from radical anti-American cleric Muqtada al-Sadr, whose emergence as a key political figure has alarmed both U.S. officials and other Shiite leaders, but others have publicly called for new names for the prime minister post.

Foreign officials for weeks have been pressing Iraqi politicians to resolve the impasse and move quickly to form a national unity government to halt the country's slide toward chaos, including suicide attacks and car bombings targeting civilians — most of them Shiites.

The Iraqi government said militants killed two people at elementary schools in a mainly Shiite district of Baghdad on Wednesday, but police in the neighborhood denied any attack occurred.

U.S. military spokesman Lt. Col. Barry Johnson also said American military teams went to both schools and found no evidence that any violent incident had taken place at either. It was unclear why the ministry released the statement.

The National Security Ministry initially said militants broke into the Amna and Shaheed Hamdi schools and "slaughtered" a teacher in each one in front of students in the Shaab neighborhood of the capital. But when questioned, the ministry later said the dead were a school guard, who was stabbed to death in front of students, and a teacher, who was shot outside the school as he arrived for classes.

Guards at both schools told an Associated Press photographer that no violence had occurred.

Lt. Col. Faleh al-Mohammedawi, spokesman of the Interior Ministry, and Ali al-Obeidi, the director of the police in the Shaab district, also said no schools in the area were attacked.

Sectarian tensions are startlingly high, a point underscored this week when clashes erupted in a Sunni Arab district of northern Baghdad over rumors that Shiite militias were coming.

At least 13 people were killed before fighting in Azamiyah ended Tuesday. Stores reopened Wednesday and residents started leaving their homes as Iraqi soldiers manned checkpoints and searched cars.

In other violence, according to police and other officials:

— Gunmen in southern Baghdad killed a construction worker, two trade ministry employees and three power plant workers who had been snatched from their car an hour earlier. At least two cars were stolen in the attacks.

— Assailants killed a medic as he walked from house to house administering vaccinations Wednesday in western Baghdad.

— Gunmen killed a 25-year-old man and wounded his brother, a science ministry employee, then killed another civilian walking down the street 15 minutes later in the capital.

— Three university professors heading back to Baghdad from Baqouba were killed by gunmen about 15 miles northeast of the capital.

— Three roadside bombs exploded in the capital, killing at least three bystanders and wounding more than 15 people, police said.

— Another bomb in Kut, 100 miles southeast of Baghdad, killed two civilians on a road near the Iranian border.

— Also in Kut, the morgue received two bodies of men, one of them handcuffed, wearing military uniforms.

— Police discovered five bodies of Iraqis in Baghdad's southeastern suburb of Rustamiyah, handcuffed and blindfolded on Wednesday. Three other bodies of government security guards, with hands and legs bound, were found near a school in Dora.

— Five foreigners, including an Egyptian, were killed late Tuesday as they drove near a village southwest of Kirkuk in northern Iraq. Officials declined to identify the nationality of the other four victims.