A US congressional report due out later today will detail September 11th intelligence failures by the FBI and CIA but will not pinpoint a "smoking gun" that could have prevented the plane attacks.
Nonetheless, Senator Bob Graham, who chaired the intelligence committee during last year's inquiry, said without the problems and with some luck, the attacks could have been prevented.
"There were enough gaffes, turf protections, and lack of the standard of professionalism that we would expect of intelligence agencies," the Florida Democrat said on CNN's Larry King Liveon Wednesday.
"If those had been eliminated plus some luck . . . we could have found out about the plotters and disrupted the plot before they struck us," Mr Graham, who is running for president, said.
The final 900-page report will include newly declassified details, but the findings of the joint inquiry of the House and Senate intelligence committees were released last December and much of the information has already been made public.
A section on whether there was any Saudi support for the hijackers will remain classified, government sources said.
The report details the contacts of an FBI informant with two of the September 11 hijackers, Khalid al-Mihdhar and Nawaf al-Hazmi, while they were living in rooms rented to them by the informant in San Diego.
The investigation raised suspicions but reached no definite conclusion about whether Omar Al-Bayoumi, a Saudi who knew the two hijackers while living in San Diego, was connected to the Saudi government, the sources said.
Prince Bandar bin Sultan, the Saudi ambassador to the United States, said in a statement on Wednesday the issue had been investigated by the United States and Britain and dismissed. Suggestions that Al-Bayoumi was an agent of the Saudi government "are baseless and not true," he said.
The congressional inquiry found the FBI and CIA missed opportunities to track or share information that could have shed light on the September 11th plot, but there was no single clue overlooked that could have prevented the attacks, according to the government sources.
One of the missed clues included the "Phoenix memo" which an FBI agent in Phoenix, Arizona, sent to headquarters, expressing concerns that al-Qaeda leader Osama bin Laden was sending students to the United States for flight training. The memo generated little interest, the joint inquiry said.
The CIA was criticised for squandering opportunities to act on information that al-Mihdhar and al-Hazmi, who were associated with bin Laden, were travelling to the United States and to add their names to US government watch lists.