Khalid Sheikh Mohammed, 9/11 plotters in court

Photo obtained March, 2003, shows, Khalid Sheikh Mohammed. The self-confessed mastermind of the 9/11 attacks and four co-accused will be formally arraigned Saturday at Guantanamo Bay, a last step before a long-awaited trial after years of legal delays

Five accused 9/11 plotters, including self-confessed mastermind Khalid Sheikh Mohammed, appeared before a military court Saturday on charges of planning the deadliest attack on US soil.

"Prosecution is ready to proceed in the case of Khalid Sheikh Mohammed," said Chief Prosecutor Brigadier General Mark Martins.

Mohammed, wearing a long beard, was seated along with his four co-plotters. Dressed in white jumpsuits and some in white skullcaps, they were uncuffed, seated at some distance from each other.

If convicted, they face the death penalty for the deaths of each of the 2,976 victims of the September 11, 2001 attacks on the United States.