The suspected ringleader of a deadly attack on the US mission in the Libyan city of Benghazi pleaded **t guilty during a brief court appearance Saturday in federal court in Washington. Ahmed Abu Khatallah was indicted by a federal grand jury during the rare Saturday session on a single charge of conspiracy to provide material support and resources to terrorists, "k**wing and intending that these would be used in preparation for and in carrying out a killing in the course of an attack on a federal facility," the Justice Department said.