Fielding questions in the House of Commons, Blair said it was still "extremely difficult" to say what remains of the Iraqi leader's regime, let alone know who should surrender to US-led forces in its name.

"There are still some very difficult things to do, and as we speak there is still intense resistance ... among those parts of Saddam's regime that want to cling on to power," he said.

"So it's not over yet."

Blair faced MPs a day after a war summit in Northern Ireland with US President George W. Bush, as British television carried vivid images of jubilation and looting in Baghdad streets.

The tone of his remarks were a reminder that, while the fall of Baghdad looked imminent, Saddam remains at large -- possibly holed up in a part of Iraq yet to be reached by coalition forces.

Earlier Thursday, Blair's official spokesman said: "We need to be careful and cautious about getting ahead of ourselves because there is localised paramilitary resistance and because command and control has broken down."

"It could be stubborn and fierce," he told reporters.

"But the (television) pictures tell their own story. And the story they tell is not just progress militarily -- which is very welcome, and we pay tribute to the troops -- but also the very real welcome local people are giving that progress."

In the Commons, Blair -- looking ahead to a European Union summit in Athens next Wednesday to be dominated by post-war Iraq and the role of the United Nations -- said it was "extremely difficult" to know what was left of "the governing higher ranks of Saddam's regime."

When asked by opposition Conservative leader Iain Duncan Smith who the coalition should accept an Iraqi surrender from, Blair replied: "It must be clear that whoever we accept ... has that proper authority."

"I cannot at the moment make a judgement as to who that may be."

On weapons of mass destruction, Blair said it was not surprising that any had not yet been found, three weeks after US and British forces invaded Iraq to overthrow Saddam.

But he added: "I have no doubt at all that these weapons of mass destruction exist... The truth is there has been a six-month campaign of concealment."

On fears of a split within the United Nations over its role in post-war Iraq, Blair said: "There are obviously going to be negotiations and discussions about this."

"It depends whether people want to reach an agreement or not."

Briefing MPs on the southern city of Basra, Iraq's second city, where British forces are concentrated, Blair said the situation was "more under control today (Wednesday) than it was yesterday" when looters ran amok

"It is not secure for our troops yet, fully," he said.

SPACE.WIRE