The Secretary of State, in consultation with the Secretary, may designate from time to time and for periods of time deemed appropriate Alternate United States Commissioners to the Commission. Any Alternate United States Commissioner may exercise at any meeting of the Commission, Council, any Panel, or the advisory committee established pursuant to section
971b of this title, all powers and duties of a United States Commissioner in the absence of any Commissioner appointed pursuant to subsection (a) of this section for whatever reason. The number of such Alternate United States Commissioners that may be designated for any such meeting shall be limited to the number of United States Commissioners appointed pursuant to subsection (a) of this section who will not be present at such meeting.