; and (B) the United States establishes a reasonable basis to believe that— (i) the identity of the potential witness is not already known to any defendant; and (ii) disclosure of the covered information to a defendant would present a threat to the safety of the potential witness or of any other person. (2) Time limit The court may delay disclosure of covered information under this subsection until the earlier of— (A) the date that the court determines provides a reasonable amount of time before the date set for trial (which shall be not less than 30 days before the date set for trial, absent a showing by the United States of compelling circumstances); and (B) the date on which any requirement under paragraph (1) ceases to exist. (3) Motions under seal The court may permit the United States to file all or a portion of a motion under this subsection under seal to the extent necessary to protect the identity of a potential witness, but the United States— (A) may not file a motion under this subsection ex parte; and (B) shall summarize any undisclosed portion of a motion filed under this subsection for the defendant in sufficient detail to permit the defendant a meaningful opportunity to be heard on the motion, including the need for a protective order or the scope of the requested protective order. (f) Waiver (1) In general A defendant may not waive a provision of this section except in open court. (2) Requirements The court may not accept the waiver of a provision of this section by a defendant unless the court determines that— (A) the proposed waiver is knowingly, intelligently, and voluntarily offered