Crawford is proceeding with charges against five other people accused of having a role in the attacks, Broyles said.
 
Prosecutors are to seek the death penalty for the men if they are found to be guilty.
 
Military tribunal

Authorities allege al-Qahtani was only prevented from taking part in the attacks because he was denied entry to the US by an immigration official.

The US military said that he had no return ticket and Mohammed Atta, the lead hijacker, was waiting for him.

Officials previously said al-Qahtani had been subject to harsh interrogation authorised by Donald Rumsfeld, the former US defence secretary.

The five defendants who are still facing charges include Khalid Sheikh Mohammed, who is alleged to have masterminded the attacks in 2001 that killed nearly 3,000 people.

The five charged men are set to be arraigned before a military tribunal at Guantanamo, where the US holds about 270 men on "suspicion of terrorism" or links to al-Qaeda and the Taliban.

Human rights organisations have criticised the rule that allows US judges to decide whether to allow evidence that may have been obtained under "coercion".

US authorities have acknowledged that Mohammed was "waterboarded" - an interrogation method designed to simulate the sensation of drowning - by CIA interrogators.

Al-Qahtani last year retracted a confession he said he made after he was tortured at Guantanamo.

In a written statement he said he was beaten, restrained for long periods in uncomfortable positions, threatened with dogs, exposed to loud music and freezing temperatures and stripped nude in front of female military staff.