((a)) A court of the United States may order the issuance of a subpoena requiring the appearance as a witness before it, or before a person or body designated by it, of a national or resident of the United States who is in a foreign country, or requiring the production of a specified document or other thing by him, if the court finds that particular testimony or the production of the document or other thing by him is necessary in the interest of justice, and, in other than a criminal action or proceeding, if the court finds, in addition, that it is not possible to obtain his testimony in admissible form without his personal appearance or to obtain the production of the document or other thing in any other manner.

((b)) The subpoena shall designate the time and place for the appearance or for the production of the document or other thing. Service of the subpoena and any order to show cause, rule, judgment, or decree authorized by this section or by shall be effected in accordance with the provisions of the Federal Rules of Civil Procedure relating to service of process on a person in a foreign country. The person serving the subpoena shall tender to the person to whom the subpoena is addressed his estimated necessary travel and attendance expenses, the amount of which shall be determined by the court and stated in the order directing the issuance of the subpoena.