Nizar Trabelsi, a Tunisian national, was arrested in Belgium on Sept. 13, 2001, two days after the Sept. 11 attacks in the U.S.
He has spent the past 12 years in custody in Belgium, where he served time on Belgian charges.
A federal indictment unsealed Thursday says Trabelsi met in the spring of 2001 with bin Laden to volunteer for a suicide bomb attack against U.S. interests.
Trabelsi appeared at a court hearing in Washington late Thursday afternoon. He pleaded not guilty through his public defender and was held without bond.
Trabelsi allegedly obtained chemicals in Europe and joined others to scout a potential target – a military facility that was used by the U.S. government and Air Force.