The men, including Khalid Sheik Mohammed, the self-proclaimed operational mastermind of the attacks, withdrew their offer to plead guilty when a military judge raised questions about whether the plea would bar them from receiving the death penalty, something the five want, The Washington Post reported.
"Are you saying if we plead guilty we will not be able to be sentenced to death?" Mohammed asked at a pretrial hearing in Guantanamo Bay, Cuba, Monday.
Also offering to plead guilty were Ramzi Binalshibh, Mustafa Ahmed al-Hawsawi, Tawfiq bin Attash and Mohammed's nephew, Ammar al-Baluchi.
"Our success is the greatest praise of the Lord," Mohammed and the others wrote of the 2001 attacks in a document sent last month to the military judge, Army Col. Stephen Henley.
The possibility that there would be no execution may have led to the men withdrawing the plea offer, attorneys said. Mohammed has expressed a desire to die as a martyr, but Henley questioned whether a death sentence could be allowed without a verdict.