upon application, may, in the discretion of the Secretary, be designated as a carrier of bonded merchandise for the final release of which from customs custody a permit has not been issued. A private carrier, upon application, may, in the discretion of the Secretary, be designated under the preceding sentence as a carrier of bonded merchandise, subject to such regulations and, in the case of each applicant, to such special terms and conditions as the Secretary may prescribe to safeguard the revenues of the United States with respect to the transportation of bonded merchandise by such applicant.