(a)

(1) Upon application of the United States, filed before return of an indictment, indicating that evidence of an offense is in a foreign country, the district court before which a grand jury is impaneled to investigate the offense shall suspend the running of the statute of limitations for the offense if the court finds by a preponderance of the evidence that an official request has been made for such evidence and that it reasonably appears, or reasonably appeared at the time the request was made, that such evidence is, or was, in such foreign country.

(2) The court shall rule upon such application not later than thirty days after the filing of the application.

(b) Except as provided in subsection (c) of this section, a period of suspension under this section shall begin on the date on which the official request is made and end on the date on which the foreign court or authority takes final action on the request.

(c) The total of all periods of suspension under this section with respect to an offense—

(1) shall not exceed three years; and

(2) shall not extend a period within which a criminal case must be initiated for more than six months if all foreign authorities take final action before such period would expire without regard to this section.

(d) As used in this section, the term "official request" means a letter rogatory, a request under a treaty or convention, or any other request for evidence made by a court of the United States or an authority of the United States having criminal law enforcement responsibility, to a court or other authority of a foreign country.