DONALD RUMSFELD refused yesterday to say when US troops would leave Iraq as his military commanders contradicted rosy White House assessments of the insurgency.

The Defence Secretary, speaking as Baghdad was engulfed by two waves of car bombings, said that it would be a mistake to schedule troop withdrawals. “It would throw a lifeline to terrorists,” he said.

Under fierce political and public pressure to show that the US was making headway in Iraq, Mr Rumsfeld said that there was a long way to go. “Success will not be easy and it will require patience,” he told the Senate Armed Services Committee.

General John Abizaid, the top US military commander in the region, said he believed that there were more foreign fighters entering Iraq to fuel the insurgency than there were six months ago. He was asked if he agreed with Vice-President Cheney, who recently declared that the insurgency was in its “last throes”. “I don’t know that I would make any comment about that other than to say there’s a lot of work to be done,” General Abizaid replied.

Last night Mr Cheney maintained that the insurgency was in its last throes, but admitted that he expected “a lot of violence, a lot of bloodshed” in the coming months. He compared the current phase of conflict in Iraq to Nazi Germany’s last stand in the Battle of the Bulge.

The exchanges came as Mr Rumsfeld made his first public appearance on Capitol Hill for several months. During that time the American public’s support for the war has fallen to its lowest level. For the first time a majority does not believe that toppling Saddam Hussein has made the US safer. Iraq, with Guantanamo Bay, is threatening to pose Mr Bush with as big a domestic headache as at any time in the past two years.

As President Bush’s support in the opinion polls has fallen, Republican congressmen, who face re-election next year, have begun to distance themselves from him. Some have accused the White House of glossing over the true picture with rhetoric. Others have demanded that he set a timetable for pulling out American troops.

Carl Levin, the senior Democrat on the committee questioning Mr Rumsfeld, said that Mr Bush should threaten to withdraw US troops unless Iraqi politicians meet the August 15 deadline for completing the country’s new constitution. Mr Levin said: “We must demonstrate to the Iraqis that our willingness to bear the burden has limits.”

Edward Kennedy suggested that Mr Rumsfeld should resign. The Democratic senator from Massachusetts said that Iraq had developed into a “quagmire” and that Mr Rumsfeld, guilty of “gross errors and mistakes”, was largely to blame. Mr Rumsfeld responded: “This is a tough business. It’s difficult, it’s dangerous, it’s not always predictable.”

In the latest violence, terrorists set off multiple, near-simultaneous, explosive devices in crowded areas of the Iraqi capital, killing almost 40 people.

At least fifteen people, including three police officers, were killed when three car bombs went off within fifteen minutes at about 7am outside a mosque in the middle-class district of Karrada. They ripped off store shutters and felled trees and market stalls as traders set up for business. Charred bodies lay in the road and a young boy, his left leg missing from below the knee, screamed on the pavement near a mangled bicycle.

Only twelve hours earlier, in the mainly Shia working-class area of Shuala, at least twenty-three people died in three explosions in a bus station and near a restaurant full of diners.

The blasts were close to the offices of the firebrand cleric Moqtada al-Sadr. Witnesses said that black-clad fighters from his al-Mahdi Army, an outlawed militia that twice fought US forces last year, blocked off streets and rounded up suspect Sunnis as police looked on.

In the chaos that followed, a group of suspected Sunni gunmen fired on an ambulance taking wounded people to hospital, then fought hospital guards for almost two hours in the precincts. The battle prevented casualties being treated and raised the death toll, a doctor said.

In the normally calm southern city of Samawah, Japanese peacekeeping troops came under rare attack when a military convoy was hit by a roadside bomb. The troops, on reconstruction work under British protection, escaped injury.

With the insurgent campaign showing no sign of abating, the al-Qaeda terrorist group of Abu Musab al-Zarqawi said that Abdullah al-Rashoud, one of Saudi Arabia’s most wanted militants, had been killed by a US air strike in the western desert city of al-Qaim on the Syrian border.

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