The letter writer to bin Laden notes that among the groups with whom they are considering cooperating, “some of their people have adopted Shiite thought, God forbid.” Al Qaeda is comprised of Sunni Muslims who see Shiites as heretics.
But he notes, again, the practicalities of such an arrangement. “They have offered funding to use, in exchange for which we are to work with them ... as a sort of propaganda; the catch being that we would conduct the operation with funding through them, and afterwards it would be announced that we cooperated with them.”