The official investigation into the September 11, 2001 attacks cast doubt yesterday on US administration claims of links between Iraq and al-Qaeda used to justify last year's invasion.

A staff report released by the national inquiry commission said there was no "credible evidence" Iraq had helped al-Qaeda to attack the US and no sign of any "collaborative relationship" between Baghdad and the group.

President George W Bush and other top officials have repeatedly cited alleged ties between al-Qaeda and Iraq, along with weapons of mass destruction that have not been found, to justify the war to bring down Saddam Hussein.

Secretary of State Colin Powell, speaking to the Arabic television station Al-Jazeera, said the administration had never implicated Iraq directly in the September 11 strikes, but refused to back down on more general links.

"I think we have said, and it is clear, that there is a connection, and we have seen these connections between al-Qaeda and the regime of Saddam Hussein and we stick with that," he said.

The commission report, issued as the panel began a final two days of hearings, said al-Qaeda chief Osama bin Laden "explored possible cooperation with Iraq" while based in Sudan in the early 1990s, even though he opposed Saddam's secular regime.

A senior Iraqi intelligence official reportedly made three visits to Sudan, meeting in 1994 with bin Laden, who requested space for training camps and help in securing weapons. "Iraq apparently never responded," the report said.

The investigation said there were also reports of contacts with Baghdad after bin Laden returned to Afghanistan in the mid-1990s "but they do not appear to have resulted in a collaborative relationship."

"Two senior bin Laden associates have adamantly denied that any ties exist between al-Qaeda and Iraq," said the report. "We have no credible evidence that Iraq and al-Qaeda cooperated on attacks against the US."

The text, which will be incorporated into a final report to be issued next month by the ten-member bipartisan panel, contrasted sharply with White House assertions on Iraq earlier this week.

Vice President Dick Cheney said Saddam had "long-established ties with al-Qaeda." Bush said Abu Mussab al-Zarqawi, an al-Qaeda-linked militant suspected of attacks in Iraq, was proof of ties between bin Laden's group and Iraqi insurgents.

While apparently clearing Iraq, the commission also disputed suggestions that Saudi officials were instrumental in financing the terrorist movement.

It acknowledged the oil-rich sheikhdom was "fertile fundraising ground," but added, "We have found no evidence that the Saudi government as an institution, or senior officials within the Saudi government, funded al-Qaeda."

The panel did point a finger at another US ally, Pakistan, for its dealings with al-Qaeda and their Afghan patrons before the September 11 strikes with hijacked airliners that left some 3 000 people dead.

"The Taliban's ability to provide bin Laden a haven in the face of international pressure and UN sanctions was significantly facilitated by Pakistani support," said the report.

"Pakistan benefitted from the Taliban-al-Qaeda relationship, as bin Laden's camps trained and equipped fighters for Pakistan's ongoing struggle with India over Kashmir."

A second report on the planning for September 11 debunked the notion it was a perfectly executed plot and said the scheme was rife with problems and internal bickering. Some senior al-Qaeda leaders even wanted to call it off.

Early versions called for the hijacking of ten planes, with a coast-to-coast list of targets including CIA and FBI headquarters and nuclear power plants. A plan to blow up several aircraft over the Pacific at the same time was scrapped.

Bin Laden had wanted to launch the US operation as early as the summer of 2000 when soon-to-be Israeli prime minister Ariel Sharon made a controversial visit to a holy site in Jerusalem, the report said. But the hijackers were not ready.

"The lesson I draw from it is that al-Qaeda is a very sophisticated, very careful, very patient, highly skilled organisation. This attack was quite a remarkable feat of planning and execution," commission vice chairman Lee Hamilton told PBS.

"All of us missed how severe this threat was."

In testimony, John Pistole, a senior FBI counterterrorism official, said the authorities had "probably prevented a few aviation attacks against both the East and West Coasts" since September 11, 2001. He did not give details.

Officials also said it was a virtual certainty that al-Qaeda would hit the US again.

"This is an enemy who is determined to do another major attack, who is determined to kill Americans and we've got to keep our guard up. We've got to be vigilant because it's coming," commission chairman Thomas Kean told PBS.

The commission is to wind up its hearings today, taking testimony on the immediate response to the attacks. The New York Times said the panel had already concluded that US air defences were woefully unprepared. – Sapa-AFP.