Unwilling to allow people it suspects of being terrorists to testify in courts, US prosecutors have sought that charges be dropped against Zacarias Moussaoui, who is referred to as the '20th hijacker'. The 9/11 terrorist attacks involved 19 hijackers.

Moussaoui (34) is a French citizen of Moroccan descent. He is the only person charged in the September 11 attacks case. He is charged with conspiring with Saudi national Osama bin Laden, the hijackers of the planes and others to carry out the 9/11 attacks.

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Moussaoui, who says his leader is Osama bin Laden, has sought permission to question some alleged Al Qaeda members to prove his innocence.

Prosecutors developed cold feet after courts granted his request. The US justice department now wants to drop charges against Moussaoui to get out of the tangle.

Among the people Moussaoui wanted to question is Khalid Shaikh Mohammed, who the US believes is a top Al Qaeda operative.

Citing security reasons, the US government has expressed unwillingness to reveal details of the statements made by alleged Al Qaeda operatives it has imprisoned at undisclosed locations outside the country. Taken into custody after the war in Afghanistan to dislodge the Taliban regime amidst efforts to locate bin Laden, it terms them as enemy combatants.