Iraq's president postponed a decision Tuesday on when to call the new parliament into session after the dominant Shiite alliance requested a delay to resolve a deadlock over the composition of the government.

Meanwhile, a new video showing three of the four hostage Christian Peacemaker activists was broadcast on Arab television, although American Tom Fox was not depicted.

A surge of sectarian violence has complicated the already snarled negotiations to form a government reflecting Iraq's main ethnic and religious communities, which the United States and its allies hope will stabilize the country so they can start pulling out troops. Scattered bombings, mortar blasts and gunfire killed another 11 people.

The senior British general in Baghdad, Lt. Gen. Nick Houghton, told The Daily Telegraph that most of Britain's 8,000 troops could be withdrawn by the middle of 2008. Britain's Defense Ministry, however, described that as just one possible scenario.

Prime Minister Tony Blair and senior government officials have consistently refused to pin down dates for ending the troop presence in Iraq, and Blair's spokesman said there were "all sorts of possible scenarios" for pulling troops out of Iraq but all depended on the conditions on the ground.

President Jalal Talabani's failed bid to order parliament into session on March 12 — the deadline set by the constitution — raised questions about whether the political process can withstand the unrelenting violence or if Iraq will disintegrate into civil war.

A political committee representing the seven Shiite parties that make up the United Iraqi Alliance, the largest group in parliament, sent Talabani a letter Tuesday asking him to delay the first session until there is agreement on who should occupy top government positions, said Khaled al-Attiyah, an independent member of the Alliance. Parliament speaker Hajim al-Hassani told reporters a new date will be set Thursday.

"Talks are still under way between the main blocs in the coming parliament," he said. "We hope that during the coming days, we will be able to reach a basic level of agreement on when to call the Council of Representatives to convene."

The talks have deadlocked over the second-term candidacy of Shiite Prime Minister Ibrahim al-Jaafari, whose most powerful supporter is the anti-American cleric Muqtada al-Sadr.

The Sunni Arab minority blames al-Jaafari for failing to control Shiite militiamen — including al-Sadr followers — who attacked Sunni mosques and clerics after the Feb. 22 bombing of a sacred Shiite shrine in Samarra. Kurds are angry because they believe al-Jaafari is holding up resolution of their claims to control the oil-rich city of Kirkuk.

Al-Jaafari said Tuesday he would not be "blackmailed" into withdrawing his candidacy, suggesting the political wrangling had grown out of a personal dispute with Talabani.

"No one can make bargains with me by enlarging personal disagreements," al-Jaafari said. Relations between al-Jaafari and Talabani were known to have soured since both men took office a year ago.

In a bid to force a showdown, Talabani, a Kurd, said Monday he would order parliament into session March 12 for the first time since the December elections and the Feb. 12 ratification of the results. Such a meeting would start a 60-day countdown for lawmakers to elect a president, approve al-Jaafari's nomination as prime minister, and sign off on his Cabinet.

Talabani was mistakenly counting on the signature of Vice President Adil Abdul-Mahdi, a Shiite, who lost his own bid for the prime minister's nomination by one vote to al-Jaafari. Talabani had in hand a power of attorney from the other vice president, Ghazi al-Yawer, a Sunni, who was out of the country.

The Shiite bloc closed ranks and Abdul-Mahdi declined to sign, for now. In an emergency meeting Monday with Talabani, seven Shiite leaders rejected the president's demand for them to abandon al-Jaafari's nomination. Talabani planned to continue the meeting Tuesday evening to try to resolve the crisis.

The president first issued the challenge March 1 in concert with Sunni Arab and some secular politicians.

"We want a prime minister who can gather all the political blocs around him, so that the government would be one of national unity," Talabani said Monday.

Shiite leaders are themselves divided over al-Jaafari's bid to remain prime minister even though they managed to come together Monday night to reject the move to drop him.

There were reports that al-Sadr, the firebrand cleric whose backing had insured al-Jaafari's nomination at the Shiite caucus last month, had threatened to order parliamentarians loyal to him to boycott the March 12 session if Abdul-Mahdi, the Shiite vice president, had signed the order to convene the legislature.

The Chicago-based Christian Peacemaker Teams said it did not know what to make of Fox's absence from the silent, 25-second video broadcast by Al-Jazeera television.

The three other hostages shown on the tape dated Feb. 28 were James Loney, 41, and Harmeet Singh Sooden, 32, of Canada; and Norman Kember, 74, of London. Al-Jazeera said the exhausted-looking men appealed to their governments to work for their release.

The previously unknown Swords of Righteousness Brigades claimed responsibility for kidnapping Fox, 54, of Clear Brook, Va., and the other activists, who disappeared Nov. 26 in Baghdad. The group said in its Tuesday statement that 14,600 Iraqis are "currently detained illegally by the Multinational Forces in Iraq."

The activists were last seen together on a video broadcast by Al-Jazeera on Jan. 28 and dated seven days earlier. At that time, Al-Jazeera reported the captors said it was the "last chance" for U.S. and Iraqi authorities to release all Iraqi prisoners, or else the hostages would be killed.

Also still held hostage in Iraq is American reporter Jill Carroll, 28, who the Iraqi interior minister has said was being held by the Islamic Army in Iraq, the insurgent group that freed two French journalists in 2004 after four months in captivity. The freelance reporter for The Christian Science Monitor was still alive, although the deadline set by her captors for the U.S. to meet their demands expired late last month.

More than 250 foreigners have been taken hostage in Iraq since the 2003 U.S.-led invasion that toppled Saddam Hussein, and at least 39 have been killed.

Iraq's political infighting has left a dangerous leadership vacuum in Iraq, underlined by the continuing violence.

Assailants attacked a Sunni mosque in the western Ghazaliyah neighborhood of Baghdad with guns and grenades Tuesday, killing a guard and torching two rooms, police said. The gunmen ambushed police when they responded, wounding five officers.

In the same neighborhood, a mortar shell wounded a worshipper leaving a Shiite mosque after dawn prayers — one of several rounds that slammed into the city.

Two bombs targeting U.S. patrols in two other neighborhoods killed at least one civilian bystander and injured five others, police said. There were no reports of American casualties.

Police said four Iraqi officers were killed in two separate attacks on police patrols in Baqouba and Beiji, north of Baghdad. The assailants were not identified.

Two car bombs exploded almost simultaneously at separate sites in the mostly Shiite city of Hillah, south of Baghdad, wounding at least three people, police said.

Gunmen shot and killed a Baghdad International Airport employee as he drove through the city, and police found four more bullet-ridden bodies — two of them with their eyes gouged out.

On Monday, snipers assassinated Maj. Gen. Mibder Hatim al-Dulaimi, the Sunni Arab in charge of Iraqi forces protecting the capital and a torrent of bombings and other shootings killed 25 other Iraqis. He was the highest-ranking Iraqi military officer killed since the the U.S.-led invasion ousted Saddam Hussein three years ago.