(CNN) -- The United States on Wednesday announced charges against Khalid Sheikh Mohammed, accused of orchestrating the September 11, 2001, terrorist attacks, and four others accused of involvement in the plot.
"If convicted, the five accused could be sentenced to death," the Defense Department said in a statement.
Along with Mohammed, the others are Walid Muhammad Salih Mubarak Bin 'Attash, Ramzi Binalshibh, Ali Abdul Aziz Ali, and Mustafa Ahmed Adam al Hawsawi.
The charges allege that the five are "responsible for the planning and execution of the attacks of Sept. 11, 2001, in New York, Washington, D.C., and Shanksville, Pa., resulting in the killing of 2,976 people," the statement said.
The five accused are charged with "terrorism, hijacking aircraft, conspiracy, murder in violation of the law of war, attacking civilians, attacking civilian objects, intentionally causing serious bodily injury, and destruction of property in violation of the law of war. The convening authority has referred all charges to a joint trial."
The convening authority, the Office of Military Commissions, referred charges to a capital military commission, the department said.
"Each of the five accused have been provided, in addition to their detailed defense counsel, learned counsel, possessing specialized knowledge and experience in death penalty cases, to assist them in their defense," the Pentagon said.
The chief judge of the Military Commissions Trial Judiciary will assign a military judge to the case, and the five will be arraigned at Naval Station Guantanamo Bay, Cuba, within 30 days of service of the referred charges upon them.
Wednesday's action is a refiling of charges against the accused conspirators. The military initially charged Mohammed in 2008, but President Barack Obama stopped the case as part of his effort to close the U.S. detention center at Guantanamo Bay.
Unable to close the center, Obama attempted to move the case to federal court in New York in 2009, only to run into a political firestorm. The plan was dropped after complaints about cost and security.
Last April, Attorney General Eric Holder announced the five would face a military trial at Guantanamo Bay.
The American Civil Liberties Union opposes the military tribunals.
They "are sure to be subject to continuous legal challenges and delays, and their outcomes will not be seen as legitimate. That is not justice," the group said Wednesday.
ACLU Executive Director Anthony D. Romero said the administration is making a "terrible mistake by prosecuting the most important terrorism trials of our time in a second-tier system of justice."
"Whatever verdict comes out of the Guantanamo military commissions will be tainted by an unfair process and the politics that wrongly pulled these cases from federal courts, which have safely and successfully handled hundreds of terrorism trials," Romero said.
"The military commissions were set up to achieve easy convictions and hide the reality of torture, not to provide a fair trial. Although the rules have been improved, the military commissions continue to violate due process by allowing the use of hearsay and coerced or secret evidence."