National security adviser Stephen Hadley said earlier this week that Bush and al-Maliki will hold talks in Amman, Jordan Wednesday and Thursday.

Bush has steadfastly stood behind the U.S. commitment to Iraq, even though growing public displeasure with the protracted war contributed significantly to Democrats retaking the House and Senate from the Republicans in the midterm elections.

A special high-level commission headed by former Secretary of State James A. Baker III is mulling recommendations for possible changes in U.S. policy in Iraq and is expected to make its findings known sometime next month.

"There was a glimmer of hope that relations between Shi'ites, Sunnis and Kurds would not be aggravated. But this factor has also been activated. Everything testifies to the fact that a critical point has been reached which threatens the disintegration of Iraq into three sectors and the start of civil chaos," Safonov said.

International terrorists and resistance not related to al-Qaida or other terrorist groups have become more active in Iraq, he said. The death sentence handed to former Iraqi leader Saddam Hussein was also a factor in the deterioration of the situation in Iraq, Safonov said. Efforts by the international community are required to settle the Iraq situation, he said.

"We were not heard or they did not want to listen when we warned of a possible deterioration. Someone oversimplified the situation. But this is no longer about that. The international community should act together for the purpose of stabilizing Iraq and efforts to find for the best way out of the situation should be consolidated," he said.

Suicide bombers ripped through a Shi'ite market in northern Iraq on Friday and mortars crashed on rival Baghdad neighborhoods, ramping up sectarian tension a day after the bloodiest bombing of the conflict killed 202 people, the Reuters news agency reports.

As political leaders pleaded for restraint and imposed a curfew on the capital to avert all-out civil war, two bombers killed 22 people at Tal Afar near the Syrian border. The Shi'ite faction that controls Baghdad's Sadr City slum, target of Thursday's attack, demanded the prime minister cancel a summit next week with U.S. President George W. Bush.

The demand was made as the people of Sadr City bore away their dead, marching behind coffins and chanting in anger and sorrow for the victims.

Moqtada al-Sadr, the young cleric whose Mehdi Army militia dominates Sadr City, told chanting supporters in a Friday sermon that the most prominent religious figure from the Sunni minority must issue a fatwa demanding an end to the killing of Shi'ites.

One of Sadr's top political aides in parliament told Reuters it would pull out of the U.S.-backed national unity government and from parliament if Shi'ite Prime Minister Nuri al-Maliki went ahead with next week's meeting with Bush in Jordan. "We have asked Maliki to cancel his meeting with Bush as there is no reason to meet the criminal who is behind terrorism in Iraq," Faleh Hasan Shanshal told Reuters. "We will suspend our membership in parliament and the cabinet if he goes ahead."

Bush has been expected to discuss with Maliki ways of giving Iraqi security forces more control to raise the prospect of U.S. troops starting to withdraw. But the competence and sectarian loyalties of the U.S.-trained Iraqi forces are in grave doubt.

Maliki is under pressure from an increasingly anxious Washington to make good on promises to disband Sadr's and other Shi'ite militias, which U.S. officials say control parts of the police and army. But the prime minister is dependent on Sadr and his fellow Shi'ite Islamists to maintain his own position.

Sadr, whose Mehdi Army rose up twice in 2004 against U.S. forces, has long demanded their withdrawal and seemed to be seeking to capitalise on the carnage in his Baghdad stronghold to press his case. Another 250 were wounded in the series of six car bombs and several mortar blasts late on Thursday afternoon.

He called for restraint from his followers, although similar public statements after the bombing of a major Shi'ite shrine at Samarra in February failed to prevent thousands of reprisal, killings much of which Sunni leaders blame on the Mehdi Army.

Many Sunnis, the dominant minority under Saddam Hussein and the source of the long insurgency against U.S. occupation, now fear a rapid withdrawal of the 140,000 American troops could unleash an all-out offensive by Iranian-backed Shi'ite militias.

"The situation is now moving to some sort of open civil war," said Iraqi security analyst Mustafa al-Alani of the Gulf Research Center in Dubai. "The situation now gradually becomes more beyond control. Neither the Americans nor the Iraqi government can control it."

Barring security forces, the only movement in the streets of the capital was the thousands of mourners as they began their journey south to the holy city of Najaf, traditional burial site for pious Shi'ites.

"At the end of the day we are all losers," said local man Hassan in Sadr City as the funeral processions passed by. "This is our home, our country. Sunnis and Shi'ites must come together to rebuild our country so we can breathe the air."

The bombings happened at around 11am (0800 BST) as funeral processions were getting under way in Baghdad for many of the more than 200 victims of attacks there yesterday.

The capital remained under a 24-hour curfew aimed at stopping revenge attacks. Hundreds of men, women and children chanted and cried as they walked beside vehicles carrying the coffins of their loved ones.

"God is great. There is no God but Allah. Muhammad is the messenger of Allah," chanted about 300 mourners as they beat their chests while walking through the Sadr City slum where the attacks happened.

The bodies were later taken for burial in the holy Shia city of Najaf, 100 miles south of Baghdad.

In the capital, followers of the radical Shia cleric Muqtada al-Sadr warned they would suspend their membership of parliament and the cabinet if the prime minister, Nuri al-Maliki, met the US president, George Bush, in Jordan next week. The al-Sadr bloc in parliament and government is the backbone of Mr Maliki's political support, and its withdrawal, if only temporarily, would be a severe blow to his already tentative hold on power.

As crews continued removing body parts from the wreckage of yesterday's car bomb attacks, tents were erected where the families of the dead could receive condolences from friends and relatives.

Three mortar rounds exploded in the Azamiya area of Baghdad at 9.45am today near the Abu Hanifa mosque, Sunni Muslims' most important shrine, wounding one guard, said the mosque's sheik, Samir al-Obaidi. The rest of Baghdad remained mostly quiet this morning, police said.

In yesterday's coordinated attacks, Sunni insurgents blew up five car bombs and fired mortars in Sadr City, killing at least 215 people and wounding 252.

Shia mortar teams quickly retaliated, firing 10 shells that badly damaged the Abu Hanifa mosque and killed one person.

Leaders from Iraq's Shia, Sunni and Kurdish communities issued a televised appeal for calm after a hastily organised meeting with the US ambassador, Zalmay Khalilzad. The Iraqi prime minister, Nuri al-Maliki also went on state television and blamed Sunni radicals and followers of Saddam Hussein for the attacks on Sadr City.

Three of the coordinated car bombings were carried out by suicide drivers; two used parked cars. Hospital corridors and waiting rooms were packed with victims of the bomb attacks, which struck at 15-minute intervals in the sprawling Shia slum. The area is a stronghold of the Mahdi army militia of the Mr Sadr.

In a TV statement read by an aide, Mr Sadr urged his followers to unite to end the US "occupation", which he said was causing Iraq's strife.

Mr Sadr said the attacks had coincided with the seventh anniversary, according to the Islamic calendar, of the assassination of his father, the Shia leader Mohammed Sadiq al-Sadr.

"Had the late al-Sadr been among you he would have said preserve your unity," the statement said. "Don't carry out any act before you ask the Hawza (Shia seminary in Najaf). Be the ones who are unjustly treated and not the ones who treat others unjustly."

However, whether Mr Sadr controls all of the gunmen who act in his name is far from clear.

Grand Ayatollah Ali al-Sistani, the pre-eminent Shia religious figure in Iraq, condemned the bombings and issued condolences to family members of the dead. He called for self-control among his followers.

Yesterday's bombings may have been carried out by Sunni gunmen seeking revenge for the kidnapping last week of up to 150 people at the Sunni-dominated ministry of higher education.

The attacks were worse than the coordinated blasts on March 2, 2004 that struck Shia Muslim shrines in Karbala and Baghdad, killing at least 181 Iraqis and wounding 573; a bombing in the southern city of Hillah that targeted mostly Shia police and national guard recruits killed 125 people and wounded more than 140 in February 2004.

On Friday radical cleric Moqtada al-Sadr's political group, which has 30 MPs in the Iraqi parliament, threatened to pull out of the government if Prime Minister Nuri al-Maliki met US President George W. Bush in Jordan on November 29.

Iraqi Shiites, many weeping, collected bodies of the victims of Thursday's bomb attacks in Baghdad's Sadr City and headed under police protection to the southern shrine city of Najaf for mass burials.

A hospital source said the toll from four car bombs that tore through the Shiite bastion had risen to 202 dead and 256 wounded, adding that the figure was expected to rise as many of the wounded were in critical condition.

The attacks prompted the interior ministry to impose an indefinite curfew in the Iraqi capital, which came into force at 8:00 pm (1700 GMT) Thursday.

Iraq also closed its two main airports, in the capital Baghdad and the southern city of Basra, as well as its southern sea ports, a senior government official said.

On Friday, the Muslim day of prayer, a deathly silence gripped the capital, with key roads and bridges empty as residents stayed indoors and vehicles remained off the streets.

In one of the squares in Sadr City, people were still collecting body parts and burying them in a grave.

They planned to build a memorial at the site to mark the most brutal attack so far against the Shiites in the conflict that followed the toppling of former president Saddam Hussein in a 2003 US-led invasion.

Almost a thousand people have been killed by violence in Iraq since Saddam was sentenced to death on November 5 for the mass killing of Shiites in the 1980s.

Angry mourners blamed followers of Saddam and Sunni leader Hareth al-Dhari, head of the Sunni Muslim Scholars' Association, for the bombings.

Dhari is currently out of Iraq, and local authorities have launched a criminal investigation against him for allegedly inciting sectarian violence.

"The government has been unable to protect us, while the Americans are arousing us to fight against each other," one angry Sadr City Shiite said.

Dozens of funeral tents were set up on streets in the district for people to offer their condolences as weeping men, women and children joined the processions heading for Najaf.

Sadr himself in his Friday sermon called on Dhari to issue fatwas to stop Sunni insurgents killing Shiites and to restrain them from joining groups such as Al-Qaeda.

A few hours before his sermon, insurgents bombed his movement's office in the restive city of Baquba. There were no casualties.

Thursday's bombings in the Shiite heartland of Baghdad are expected to further deepen the rift between the two warring communities.

Premier Maliki appealed for calm but said the attacks posed a grave threat.

"This crime reflects serious danger on Islamic brotherhood by terrorists who are trying to trigger sectarian strife," Maliki said.

Parliamentarian Mahmud Othman said he expected a Shiite backlash.

"There will be a strong reaction to these bombings. Already there are reports of Sunni neighbourhoods being attacked last night (Thursday) and the sectarian rift between the two will deepen further," he told AFP.

In the aftermath of the attacks, 13 mortar rounds slammed into Adhamiyah, a Sunni neighbourhood, wounding 10 people. On Friday, nine more mortar shells fell in northwest Baghdad near the Sunni mosque of Umm al-Qura, headquarters of the hardline Sunni Muslim Scholars' Association.

Othman blamed the growing bloodshed on the country's politicians.

"Leaders from both sides are trading accusations against each other. There have been no meetings between them for (a long time now). How do you expect reconciliation at a national level when it does not exist between them?"

Commenting on the Sadr City bombings, the United Nations Special Representative to Iraq, Ashraf Qazi, said "these crimes can widen the sectarian divide and thrust the country into a cycle of uncontrollable violence threatening the very social fabric of Iraq".

Sadr's group threatened to withdraw from the government if Maliki met Bush, and demanded that the government "specify the nature of its relations with the occupation forces". It also repeated calls for a timetable to pull coalition troops out of Iraq.

Bush and Maliki are expected to discuss new strategies aimed at stopping the bloodshed in Iraq when they meet in Jordan.

They also open up the possibility that many troops will be returning home by the time Mr Blair resigns.

Such a development might free up some troops for Afghanistan, where proposals are being drawn up by the military for reinforcements to combat a potential Taliban offensive in the spring.

Ms Beckett and No 10 stressed that the timetable was dependent on the continued good progress of a joint British-Iraq operation in Basra, the largest and most populous of the four provinces originally put under British control. Britain has already relinquished control of two provinces and stood back from frontline security in a third.

Ministry of Defence sources said most of Britain's 7,200 troops in the region would initially be withdrawn from the streets and then pulled back to the Basra airbase. An increasingly residual force would be prepared to re-enter the Shia-controlled city to restore order.

Troops might then be shifted to bases in friendly neighbouring countries.

Ms Beckett's announcement comes against a backdrop of pressure from senior military figures, including General Sir Richard Dannatt, chief of the general staff, who has said that the UK's continued presence has exacerbated security problems.

Sir Menzies Campbell, the Liberal Democrat leader, said yesterday he was convinced the British military were now advising the government they had done all they could there.

Yesterday, the foreign secretary told MPs: " Although there can be no question of us abandoning Iraq in the present circumstances, that does not mean that things are standing still. Our approach has evolved significantly in recent months in response to a dynamic situation."

She said Iraq's prime minister, Nouri-al Maliki, was determined to take increasing control of security.

British and Iraqi troops are halfway through Operation Sinbad, the attempt to divide the city into 18 areas and overhaul each one in turn by giving widespread access to drinking water, clearing streets and improving job opportunities.

Major General Richard Shirreff, the British commander in southern Iraq, has said a "reasonable reduction" in the 7,000-strong force in southern Iraq was possible at the end of the operation in February.

Defence officials said last night that the work was "going well" and that clashes between rival Shia militia in Amara, capital of Maysan province, north of Basra, were stopped by Iraqi forces. The British troops on standby were not needed.

Overall, violence has been falling in the city, but the position is unstable and dependent on the wider political situation in Iraq and the speed with which the local police force can be trained. It is still seen as corrupt and penetrated by militias.

Des Browne, the defence secretary, said it was neither appropriate nor helpful to speculate on British troop planning. A defence source said it might still be impossible for troops to leave altogether for at least a year.

It is also likely that any decisions will also need to be coordinated with the Americans. Different security considerations apply in the rest of Iraq, and decisions will await political discussions arising from the bipartisan Baker report due by the end of the year.

William Hague, the shadow foreign secretary, said a withdrawal would also depend on the state of the civilian police forces in the country.

The Conservatives are also putting increasing pressure on the government to spell out its plans for Afghanistan ahead of the Nato summit in Riga next week.