A year before the 9/11 attacks a secret US intelligence unit had identified four of the hijackers as likely linked to al-Qaeda, a US congressman says.
The remarks will fuel controversy over missed chances to prevent 9/11
But the unit's request for the FBI to be informed was turned down, according to Representative Curt Weldon.
One of the men identified was said to be 9/11 ringleader Mohammed Atta.
Mr Weldon has a reputation for bold statements, but his comments are being taken seriously after claims from an unnamed former intelligence official.
The New York Times quotes the official as saying the programme - named Able Danger - was set up in secret by the US military's Special Operations Command.
"Ultimately, Able Danger was going to give decision makers options for taking out Al-Qaeda targets," the former official said.
The paper also said the former spokesman for the 9/11 Commission, Alvin Felzenberg, confirmed that members of its staff were told in 2003 about the military programme.
US military officials were not able to confirm the existence of the unit.
But Mr Weldon's remarks will fuel controversy over the opportunities that were missed by US government agencies to prevent the 9/11 attacks.
He spoke publicly about the issue on 27 June in a little-noticed speech on the house floor, and to a local paper in his Pennsylvania constituency.
He says the unit prepared a chart that included visa photographs of the four men and recommended to Special Operations Command that the FBI be informed.
The course of action was said to have been rejected in part because the men were in the US on valid entry visas.