The Secretary of State may pay, without regard to section 5702 of title 5, subsistence expenses of (1) special agents of the Department of State who are on authorized protective missions, whether at or away from their duty stations, and (2) members of the Foreign Service and employees of the Department who are required to spend extraordinary amounts of time in travel status. The authorities available to the Secretary of State under this section with respect to the Department of State shall be available to the Broadcasting Board of Governors and the Administrator of the Agency for International Development with respect to their respective agencies, except that the authority of clause (2) shall be available with respect to those agencies only in the case of members of the Foreign Service and employees of the agency who are performing security-related functions abroad.