A former FBI translator with top-secret security clearance says she has provided detailed information to the panel investigating September 11 that proves senior officials knew of al Qaeda plans to attack the US with aircraft months before the strikes in New York and Washington.
She said national security adviser Condoleezza Rice's claim that there was no such information is "an outrageous lie".
Sibel Edmonds said she spent more than three hours in a closed-door session with the commission's investigators providing information circulating within the FBI in the spring and summer of 2001 suggesting an attack using aircraft was just months away and the terrorists were in place.
The Bush Administration, meanwhile, has sought to silence her and has obtained a gag order from a court by citing the rarely used "state secrets privilege".
She told the Independent: "I gave [the commission] details of specific investigation files, the specific dates, specific target information, specific managers in charge of the investigation. I gave them everything [so] that they could go back and follow up.
"This is not hearsay. These are things that are documented. These things can be established very easily."
She added: "There was general information about the time frame, about methods to be used - but not specifically about how they would be used - and about people being in place and who was ordering these sorts of terror attacks. There were other cities that were mentioned. Major cities - with skyscrapers."
The accusations of Edmonds, a Turkish-American who speaks Arabic, Farsi, Turkish and English, will reignite the controversy over whether or not the Bush Administration ignored warnings about al Qaeda. That controversy was sparked most recently by Richard Clarke, a former senior counter-terrorism official, who has accused the Administration of repeatedly ignoring his warnings about the threat posed by al Qaeda in the months after President Bush assumed office.
This issue - what the Administration knew and when - is central to the investigation being carried out by the 9-11 Commission which has been hearing testimony in both public and private from Government officials, intelligence officials and secret sources. Earlier this week, the White House undertook a major U-turn when it said Rice would appear in public before the commission to answer questions. Bush and his deputy Dick Cheney will also be questioned in a closed-door session.
Edmonds, 33, from northern Virginia, was hastily hired as a part-time translator for the FBI's Washington field office on September 13, 2001, just two days after the al Qaeda attacks that killed almost 3000 people. Her job was to translate documents and recordings from FBI wire-taps, some of which had already been translated and some of which was new.
She said much of the information relating to the terror attacks - particularly about the funding of the operation - was not obtained from agents working strictly in counter-terrorism but in areas such as money-laundering.
"President Bush said they had no specific information about September 11 and that is accurate but only because he said September 11," she said.
There was, however, general information about the use of aeroplanes and that an attack was just months away.