US forces were reduced to near-impotent bystanders as the violence ignited by Thursday’s car bomb attacks on Shi’ite targets in Baghdad spawned a spiral of revenge.

After a series of attacks on Sunni mosques on Friday, insurgents in Diyala province were reported yesterday to have stormed two Shi’ite houses and murdered 21 men in front of their relatives. A suicide car bomber yesterday attacked a joint US-Iraqi checkpoint near Fallujah, killing three civilians and one American soldier.

US and Iraqi troops also killed 22 insurgents and an Iraqi civilian, and destroyed a factory being used to make roadside bombs, during raids north of Baghdad yesterday.

The violence closed Baghdad airport and forced the cancellation of a planned trip to Iran by Jalal Talabani, the Iraqi president, who was hoping to enlist the help of the Shi’ite regime in Tehran in quelling the sectarian strife.

More than 200 people, most of them Shi’ites, were killed in Thursday’s attacks in the Baghdad slum of Sadr City, a stronghold of Moqtada al-Sadr, the radical Shi’ite cleric whose Mahdi Army is regarded by Washington as a threat to democratic rule.

Maliki’s fragile coalition depends on the support of Sadr and his allies. But the cleric’s aides last week blamed America for the violence and warned the prime minister that Sadr would withdraw from the government if Maliki meets Bush in Jordan on Thursday.

The descent of Iraq into open sectarian warfare left both men facing difficult choices in the wake of US midterm elections that showed growing support for American withdrawal. The White House insisted that this week’s summit would go ahead and that “gaining control of the violence” would be top of the agenda.

The assassination of Pierre Gemayel, the Lebanese government minister, last week and reports that Syria and Iran have re-armed Hezbollah militants since this summer’s battle with Israel, have contributed to a sense that America is not just losing the war in Iraq but in danger of losing the entire region.

“I think Iran senses an opportunity to deliver a knock-out punch to the United States,” said Michael O’Hanlon, a regional specialist at the Brookings Institution. “They may see a chance that the US is driven out of the region altogether. Iran could become the great power of the Persian Gulf.”

Last week Baghdad witnessed some of the worst atrocities since the fall of Saddam Hussein. On Friday, suspected Shi’ite militiamen seized six Sunnis as they left prayer services in Hurriyah and burned them alive.

“They threw handgrenades at houses and shops in the street,” said Emad al-Hashemi, a resident who saw the gunmen jump out of a convoy of four-wheel drive vehicles. “They followed people into the mosques and pulled out six civilians and poured petrol over them and set fire to them.”

If Bush succeeds in meeting Maliki this week, he will urge him to disarm the Shi’ite militias. But Maliki appears to have neither the military muscle nor the political will to persuade Sadr to lay down his arms.

In an attempt to rally support from America’s traditional allies in the region, Bush yesterday dispatched his vice-president, Dick Cheney, to Saudi Arabia, where the royal family has become increasingly perturbed at the chaos close to their borders.

The president is awaiting the results of two separate reviews of policy in Iraq, one by the Pentagon, the other led by former secretary of state James Baker, who is expected to recommend negotiations with Iran and Syria.

Steven Cook, of the New York-based Council on Foreign Relations, said the main purpose of Bush’s visit to the region was to show angry American voters that he was at last preparing an exit strategy. “But our ability to effect political developments [in the region] is limited,” Cook said.

Other US analysts described the planned summit as “an act of desperation”. An American strategy that began with bold promises of a democratic transformation of the region has been reduced, in O’Hanlon’s words, to “just trying to prevent things from getting worse”.

Additional reporting: Hugh Macleod, Damascus

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