A phone call between the alleged masterminds of the September 11 attacks was intercepted by a western intelligence agency seven weeks before the terror act, it has been revealed.
Agents listened to a call between Khalid Sheikh Mohammed, the alleged ringleader, and Ramzi Binalshibh, another plotter, on July 20 2001.
A newly released 9/11 commission document, which had previously been in part redacted, reveals details of a U.S. Department of Justice briefing on March 18 2004 when the call was discussed.
Plotters: Documents reveal that intelligence agents listened to a call between Khalid Sheikh Mohammed, left, and Ramzi Binalshibh on July 20 2001
'There was a call between KSM [Khalid Sheikh Mohammed] and Binalshibh,' the document notes.
'There is a discussion about Teresa being late, which refers to Jarrah and possible conflicts with Atta.'
The plotters were worried that one of the plane hackers, Ziad Jarrah, might pull out of the attacks. Mohammed Atta was another of the hijackers.
The document was obtained by Anthony Summers and Robbyn Swan for their book 'The Eleventh Hour', about the attacks.
Mr Summers said it is further evidence of significant warnings of the attacks.
Intercepted: The phone call was traced seven weeks before the September 11 2001 terror attacks on the World Trade Center
Hijackers: The plotters discussed Ziad Jarrah, left, and Mohammed Atta
'The questions are which intelligence agency intercepted this call and what was done with the information,' he told the Sunday Times.
Both Khalid Sheikh Mohammed and Ramzi Binalshibh are awaiting trial at Guantanamo Bay.
They face the death penalty if convicted.
Khalid Sheikh Mohammed was arrested in Pakistan in 2003.
'WE ARE FLYING WAY TOO LOW': THE PANICKED CALLS FROM 9/11 FLIGHTS REVEALED
Revealed: Transcripts of calls from the first plane to hit the towers were released
Author Anthony Summers has also obtained the transcripts of conversations between flight crew, ground staff and the military during the attacks.
They include poignant calls for help from flight 11, the first plane to hit the twin towers in New York, and American Airlines ground crew monitoring the situation.
American Airlines employee Nydia Gonzalez said: 'The number five [a member of the air crew] has been stabbed. She seems to be breathing.
'The number one [another air crew member] has been stabbed pretty badly. She's lying down.'
Moments before the plane crashed into the north tower of the World Trade Center, Amy Sweeney, a flight attendant, said: 'We are in a rapid descent. We are all over the place.
'I see the water. I see the buildings. We are flying way too low. Oh my God we are way too low.'