The US has issued formal charges against the alleged mastermind of the September 11 attacks, Khalid Sheikh Mohammed, and four suspected co-conspirators.
The Pentagon says they will be tried by a military tribunal at Guantanamo Bay.
The men are accused of terrorism, hijacking aircraft, conspiracy, murder in violation of the law of war, and other counts. If convicted they could face the death penalty.
The US authorities believe Mohammed co-ordinated the 9/11 attacks and transferred money used to pay for the hijackings.
A previous plan to try the men in New York City prompted a public outcry.