During any period in which vessels may be requisitioned under this chapter, the President is authorized and empowered through the Secretary of Transportation to purchase, or to requisition, or for any part of such period to charter or requisition the use of, or to take over the title to or possession of, for such use or disposition as he shall direct, any merchant vessel not owned by citizens of the United States which is lying idle in waters within the jurisdiction of the United States and which the President finds to be necessary to the national defense. Just compensation shall be determined and made to the owner or owners of any such vessel in accordance with the applicable provisions of this chapter. Such compensation hereunder, or advances on account thereof, shall be deposited with the Treasurer of the United States in a separate deposit fund. Payments for such compensation and also for payment of any valid claim upon such vessel in accord with the provisions of section 56305, shall be made from such fund upon the certificate of the Secretary of Transportation.