Prosecutors say Moussaoui was to have been the 20th hijacker
Lawyers for the US Government have asked a judge to dismiss all charges against a man accused of conspiring in the 11 September attacks.
Zacarias Moussaoui, who admits to being a member of al-Qaeda, is the only person in the US to have been charged in connection with the plot.
Correspondents say the extraordinary request by prosecutors is a legal manoeuvre, designed to stop Mr Moussaoui's access to high-level al-Qaeda suspects being interrogated in secret locations by the US military.
It follows a decision by the judge handling the case that Mr Moussaoui should have access to the three suspects so he can prove he was not linked to the 11 September plot and avoid the death penalty.
The judge said he should be allowed to interview the men because they may have information that could spare his life.
The justice department says allowing an avowed terrorist access to enemy combatants in the midst of a war would harm national security.
The government has refused to comply with the ruling, leaving the judge with no alternative but to impose a punishment on prosecutors.
The BBC's Ian Pannell, in Washington, said that what government lawyers have now suggested is a clever legal move. They have called on the judge to throw the case out.
It would not mean that Moussaoui would be released from custody; instead, prosecutors would then go straight to a higher court and appeal the dismissal and crucially, the original ruling that Mr Moussaoui should get access to the al-Qaeda detainees.
The US Government regards Mr Moussaoui, a 35-year-old French citizen of Moroccan origin, as the "20th hijacker". It accuses him of conspiring with the 19 other men alleged to have carried out the attacks on New York and Washington.
He was arrested on immigration charges three weeks before the suicide hijackings on 11 September 2001 after he aroused suspicions at a flight school in Minnesota.
He is charged on four counts that carry the death penalty in the case of conviction - conspiracy to commit acts of terrorism, to commit aircraft piracy, to destroy aircraft and to use weapons of mass destruction.
He is also charged with conspiracy to kill US Government officials and destroy US Government property - two lesser charges.
The US authorities have not offered evidence of a direct link between him and the hijackings and some legal experts have said that the evidence against Mr Moussaoui is circumstantial.