As US Marines and Iraqis joined forces to topple a statue of Saddam Hussein in downtown Baghdad, Vice President Dick Cheney cited "evidence of the collapse of any central regime authority" but warned "hard fighting" may yet lie ahead.

Television images of joyous Iraqis mobbing US soldiers "are heartening signs of military progress and mankind's taste for freedom," White House spokesman Ari Fleischer told reporters. "It's a historic moment."

But "we are still in the midst of a shooting war, and men and women are still in harm's way. The war is not over. There remain a lot of dangers ahead," the spokesman said as gunfire could be heard on broadcasts from Baghdad.

Fleischer said that other cities in Iraq remain under the control of Saddam's regime and that US-led forces still face pockets of tough resistance, adding: "This remains a time of utmost caution."

The subdued tone of the White House stood in stark contrast to the jubilation shown on television as Iraqis assailed statues and portraits of Saddam and other symbols of his iron-fisted rule three weeks to the day after Bush gave US-led forces the order to go to war.

"As much as the president is pleased to see the progress of the military campaign, and the Iraqi people finding freedom where they are finding it, he remains very cautious because he knows that there is grave danger that could still lie ahead," said Fleischer.

Asked about conflicting media reports about whether Saddam was alive or dead, Fleischer said that "we still don't know his fate" but cautioned neighboring nations against offering him refuge.

Saddam "missed his chance" to go peacefully into exile, he said, adding that Bush "gave him an opportunity and he did not take it," an apparent reference to the US leader's 48-hour exile or war ultimatum some three weeks ago.

Cheney, speaking to an audience of newspaper editors in New Orleans, refused to predict how long the fighting will last in Iraq.

Last week, Fleischer had said that Bush's "definition of victory" was the point at which the regime is disarmed and its hold on power is broken "so the Iraqi people can be free and liberated."

US forces met little Iraqi resistance as they took over swathes of Baghdad, with looting erupting as it became clear that Saddam's 24-year stranglehold on the Iraqi people was disintegrating.

To do away with a giant statue of Saddam in Al-Fardus (Paradise) Square, US soldiers slung a thick rope noose around the Iraqi leader's neck, and briefly draped the Stars and Stripes over his head.

Civilians queued up to hammer blow after blow into the plinth supporting the statue, while nearby soldiers chatted to journalists, the hatches of their tanks open, although other marines on foot took up precautionary positions.

SPACE.WIRE