Any citizen of the United States or any shipyard of the United States may make application to the Secretary of Transportation for a construction-differential subsidy to aid in reconstructing or reconditioning any vessel that is to be used in the foreign commerce of the United States. If the Secretary of Transportation, in the exercise of his discretion, shall determine that the granting of the financial aid applied for is reasonably calculated to carry out effectively the purposes and policy of this chapter, the Secretary of Transportation may approve such application and enter into a contract or contracts with the applicant therefor providing for the payment by the United States of a construction-differential subsidy that is to be ascertained, determined, controlled, granted, and paid, subject to all the applicable conditions and limitations of this subchapter and under such further conditions and limitations as may be prescribed in the rules and regulations of the Secretary of Transportation has adopted as provided in section
1114
(b) of this Appendix; but the financial aid authorized by this subsection shall be extended to reconstruction or reconditioning only in exceptional cases and after a thorough study and a formal determination by the Secretary of Transportation that the proposed reconstruction or reconditioning is consistent with the purposes and policy of this chapter.