President Bush has said that the US remains committed to the June 30 deadline for handing power over to the Iraqis despite some of the bloodiest violence since the official end of hostilities almost a year ago.

More than 50 Iraqis, eight US troops and an El Salvadoran soldier have been killed in two days of fierce clashes. A total of 85 Iraqis and 24 American troops were wounded in running street battles.

The violence has been blamed on the followers of Moqtada al-Sadr, a radical Shia Muslim cleric. A warrant has been issued for al-Sadr's arrest.

President Bush said today: "This is one person (al-Sadr) that is deciding that rather than allowing democracy to flourish, he's going to exercise force. We just cannot let it stand.

"This is a person and followers who are trying to say we don't want democracy, as a matter of fact, we'll decide the course of democracy by the use of force, and that is the opposite of democracy."

He also sought to reassure Iraqis that the US would not leave until peace had been restored to the country.

He added: "The message to the Iraqi citizens is, they don't have to fear that America will turn and run. And that's an important message for them to hear. If they think that we're not sincere about staying the course, many people will not continue to take the risk towards freedom and democracy."

Senior members of the US Congress publicly questioned yesterday whether the deadline for handover to Iraqi sovereignty was realistic.

Tony Blair's official spokesman also said there was "no change" in their determination to hand over power to the Iraqis on June 30.

Earlier, US troops attacked armed Shia Muslim groups in Baghdad and sealed off the town of Fallujah.

Apache helicopters in Baghdad sprayed fire on units of the Mehdi Army, the private militia of al-Sadr that had attacked US soldiers and Iraqi paramilitaries trying to enter the al-Shula district.

The helicopter strike is thought to be the first of its kind in Baghdad since the war that toppled Saddam Hussein.

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