In the case of any individual who has been or who may be called to testify or provide other information at any proceeding before an agency of the United States, the agency may, with the approval of the Attorney General, issue, in accordance with subsection (b) of this section, an order requiring the individual to give testimony or provide other information which he refuses to give or provide on the basis of his privilege against self-incrimination, such order to become effective as provided in section 6002 of this title.