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.