President Bush was under mounting pressure last night after it was revealed he had been warned a month before 11 September of an al-Qa'ida plot to hijack American airliners.
There were widespread demands for a full inquiry into why his administration alerted law enforcement agencies but did not make the warning public or take greater preventive measures.
Mr Bush and his senior advisers were told of the threat, involving terrorists linked to Osama bin Laden, by means of a daily intelligence briefing in the first week of August, passed to Mr Bush while he was on holiday at his Texas ranch.
The CIA warning, which was highly classified, was not specific in terms of dates or locations and there was no mention that the hijackers intended to use the aircraft as weapons, as they did with devastating effect in the attacks on New York and Washington.
But while the warning may not have been specific, there was fierce criticism in Washington yesterday that Mr Bush's senior intelligence advisers had failed to "join the dots" by linking various pieces of intelligence that suggested an attack was imminent.
"There should have been bells and whistles going off," said the Democrat John Edwards, a member of the Senate Intelligence Committee. "Was this information communicated to a central source? Was action taken?"
Disclosure of the warning led to a flurry of questions about exactly what, and when, Mr Bush was told. There was also a growing feeling that the President – still enjoying approval ratings of almost 70 per cent – could be damaged by the revelation.
The White House – forced on to the defensive for the first time over the 11 September attacks – claimed it had taken "all appropriate action", alerting US embassies and military facilities and sharing information about the threats with domestic agencies.
"Throughout the summer, beginning in May, the government received heightened reporting on threats to United States' interests or territory, most of it focused on threats abroad," Mr Bush's spokesman, Ari Fleischer, said.
"As a result, several actions were taken to button down security. All appropriate action was taken based on the threat information that we had. The President did not – not – receive information about the use of airplanes as missiles by suicide bombers. This was a new type of attack that was not foreseen."
One investigator told The New York Times that over the 4 July holiday there had been "a lot of static in the system suggesting something was coming". After that, the "evidence" disappeared as quickly as it had arrived before the new warning in August.
It has also been revealed that the FBI received a memo written by a Phoenix-based field agent in July last year warning of a link between a group of Middle Eastern aviation students and al-Qa'ida.
Leading Democrats asked why the various warnings were not put together and more proactive measures taken.Tom Daschle, the Senate majority leader, said he was "gravely concerned" about the issue. Dick Gephardt, the House minority leader, said: "You cannot say that we did everything we could. Let's do better next time."Reuse content