In the run up to 9/11, high ranking CIA officials, including the Director of Central Intelligence (head of the CIA), George Tenet, were aware that two of the 9/11 hijackers had entered America in the year 2000. However, they withheld this information from the FBI and "more or less lied" about it to the US Congress and the 9/11 Commission in the aftermath of the attacks on the World Trade Centre and the Pentagon.
Richard Clarke, a former counter-terrorism adviser to the Bush administration contends that this information was deliberately suppressed - and that the information could have prevented the 9/11 attacks.
Editor's Note: In an interview with Democracy Now, Lawrence Wilkerson, who was chief of staff to America's former Secretary of State, Colin Powell, argues that Tenet also provided what later turned out to be false intelligence about the existence of weapons of mass destruction in Iraq. This information ultimately laid the foundation for the invasion of Iraq when the Bush administration also falsely alleged ties between Al Qaeda and Saddam Hussein. Wilkerson says that he would be willing to testify against former vice president of America, Dick Cheney, if he were ever put on trial.
You might also be interested in two other interviews from the Real News Network, which contend that Saudi involvement in the 9/11 attacks is being suppressed: Suppressing investigation about the role of Saudi Arabia in 9/11 and 9/11 and Who Rules Saudi Arabia. Former US Senator, Bob Graham, interviewed by Democracy Now, also highlights the role of the Saudis. He calls for President Obama to reopen the investigation into the Saudi role in the 9/11 attacks.