Deals with Mohammed and two alleged accomplices were announced on July 31 but sparked anger among some relatives of those killed on September 11, 2001, as well as criticism from leading Republican politicians, and Austin scrapped them two days later.

"The families of the victims, our service members and the American public deserve the opportunity to see military commission trials carried out in this case," Austin told journalists during a news conference in Annapolis.

The cases against the 9/11 defendants have been bogged down in pre-trial maneuverings for years, while the accused remained held at the Guantanamo Bay military base in Cuba.

The terms of the deals were not made public, but the New York Times reported that Mohammed, Walid bin Attash and Mustafa al-Hawsawi had agreed to plead guilty to conspiracy in exchange for a life sentence, instead of facing a trial that could lead to their executions.

Much of the legal jousting surrounding the men's cases has focused on whether they could be tried fairly after having undergone methodical torture at the hands of the CIA in the years after 9/11 -- a thorny issue that the plea agreements would have avoided.