The court, upon a sufficient showing, may authorize the United States to delete specified items of classified information from documents to be made available to the defendant through discovery under the Federal Rules of Criminal Procedure, to substitute a summary of the information for such classified documents, or to substitute a statement admitting relevant facts that the classified information would tend to prove. The court may permit the United States to make a request for such authorization in the form of a written statement to be inspected by the court alone. If the court enters an order granting relief following such an ex parte showing, the entire text of the statement of the United States shall be sealed and preserved in the records of the court to be made available to the appellate court in the event of an appeal.