President Bush's CIA briefing last August about possible attacks on US targets by al-Qa'ida – the focus of the current "what did he know and when did he know it" furore – was based on British intelligence reports, officials on both sides of the Atlantic said.
Intelligence sources in London confirmed yesterday that both MI5 and MI6 had sent reports to the United States in the run-up to 11 September, suggesting that America was under threat.
The reports did not mention a specific plan or method of attack, however, and speculated that the most likely targets were overseas American interests such as embassies or military bases.
In Washington, meanwhile, government officials spoken to by The New York Times suggested Mr Bush's briefing on 6 August at his ranch in Texas was a rehash of 1998 intelligence data "drawn from a single British source".
Both the unnamed officials and Condoleezza Rice, the National Security Adviser, said the report contained speculation that Osama bin Laden's organisation might be thinking of hijacking planes, but there was no hint that they might be used as weapons of mass destruction in a suicide mission.
Ms Rice said in a news briefing on Thursday: "It [the report] mentioned hijacking, but hijacking in the traditional sense ... The most important and most likely thing was that they would take over an airliner holding passengers and demand the release of one of their operatives."
US law enforcement has repeatedly received word over the past few years of plans to try to spring Omar Abdel Rahman, the so-called "Blind Sheikh", from federal prison where he is serving a life sentence for his role in plotting a bomb attack on the World Trade Centre in 1993.
It was not clear from Ms Rice's words whether he was the "operative" she was referring to, but in any case she made clear that the speculation was based on long-standing thinking in the intelligence community, not new data.
"It was an analytic report that talked about UBL's [Mr bin Laden's] methods of operations, talked about what he had done historically," Ms Rice said. "I want to reiterate: it's not a warning. There's not specific time, place or method mentioned."
Barring the emergence of documentary evidence contradicting the official line – and none has so far come to light – it seems hard to argue that Mr Bush was negligent in his handling of the information he received.
According to Ms Rice's account, there was a great deal of nervousness about terror attacks in the early part of last summer, but the focus was on preventing possible attacks on the G8 summit in Genoa.
There was also specific concern about US interests in Paris, Rome and Turkey, which has since been substantiated by the arrest of numerous suspected al-Qa'ida operatives believed to have been planning assaults on the US embassies in France and Italy and an American military base in Turkey.
The most damning evidence of negligence pre-11 September remains, for the moment, below White House level, with the Federal Bureau of Investigation, the Central Intelligence Agency and immigration officials, who had a tantalising string of leads that they failed to follow up or pass on to their political masters.
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