Khalid Sheik Mohammed, a Guantanamo Bay prisoner who officials say has bragged he was behind the attacks, agreed to be a defense witness in the New York trial of Sulaiman Abu Ghaith, a son-in-law of al-Qaida founder Osama bin Laden.
Abu Ghaith is likely to be the only person who goes on trial -- beginning next week -- in New York in the Sept. 11 attacks.
Mohammed agreed in a Jan. 27 letter to be interviewed by Abu Ghaith's defense attorneys with the condition that federal prosecutors and military lawyers aren't allowed to listen in or monitor the conversation.
A compromise was reached Thursday in which Abu Ghaith's lawyer would submit written questions to Mohammed and government lawyers would be able to review the questions and answers to make sure no classified material was included, the Los Angeles Times reported.
If national security officials approve of Mohammed's replies, he could provide testimony during Abu Ghaith's trial on a closed-circuit feed from Guantanamo Bay, the newspaper said.