Soldiers with the Fourth Infantry Division (4ID), a 30,000-strong task force which will flow into Iraq over the coming days, insist that although the war is won the peace could still be lost unless security is re-established across the country.

Commanders are receiving daily intelligence updates on Iraqi irregular forces which are expected to mount a low-level guerrilla campaign against any future pro-US government in Baghdad.

These include remnants of Saddam Hussein's diehard Fedayeen militia and suicide bombers which have claimed the lives of eight US soldiers in three blasts since the war began on March 20.

Even more than the prospect of combat, the responsibility for winning the peace in an environment where friends may be indistinguishable from foes is weighing heavily on the minds of some of the young soldiers here.

"It's something you just don't want to think about: will I pull the trigger or not?" said 19-year-old Dennis Hernandez, a specialist in an infantry battalion, when asked what he would do if a civilian car failed to stop at a checkpoint.

"It's a challenge for the infantry guys down on the ground because they are the ones who have to decide whether to shoot or not to shoot."

Officers are emphasising with the troops that the military successes of their comrades could be undone if the follow-up stabilisation forces fail to restore order and win the confidence of the Iraqi people.

"These 18 to 20-year-old kids have to understand that the army and the United States of America will be held accountable by what they do over there," said Captain Anthony Mullinax.

"All the progress we've made in Iraq could suddenly be nullified by poor judgement, but I'm sure they're trained well enough and they'll know how to react to the situation."

Widescale looting and sporadic fighting has complicated the delivery of badly-needed humanitarian supplies to much of Iraq, a country already on its knees after three wars and more than 12 years of UN-imposed sanctions.

The 4ID's rules of engagement are still designed for combat, but senior officers said they anticipated a change commensurate with what commanding officer General Ray Odierno has described as a stabilisation and security operation.

Lieutenant Colonel John Miller, commander of the 2-8 Infantry Battalion, said he expected to see Iraq divided into military regions in the manner of Bosnia and Kosovo, with security issues being assigned to different US divisions.

"The first rule of engagement for American soldiers is that you always have the right of self-defence, but it has to be proportional. You have to have a bit of patience and be able to back up and assess the situation," said Miller, a veteran of the 1991 Gulf War and the NATO-led peacekeeping mission in Bosnia.

But he insisted that without a ceasefire or formal declarion of surrender by Saddam's regime, the 4ID's primary focus remained dealing with "non-compliant forces" rather than providing humanitarian or civil services.

There has been growing anxiety inside Iraq over Washington's plans to arrange a new administration amid ongoing looting and occasional fighting following the collapse of Saddam's regime last week.

Pentagon officials are now saying that with the war virtually over, forces are starting to move out of the region and attention is shifting to the massive task of rebuilding.

The 4ID, the US army's most modern "digital" division, was originally scheduled to enter Iraq from the north but Turkey refused to grant permission.

Lead elements crossed into southern Iraq from Kuwait in recent days, but most of the division's Abrams tanks and Bradley fighting vehicles are still being marshalled in the desert here.

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