The Secretary may issue obligations to the Secretary of the Treasury in an amount outstanding at any one time sufficient to enable the Secretary to carry out his obligations under guarantees authorized by this section. The obligations issued under this subsection shall have such maturities and bear such rate or rates of interest as shall be determined by the Secretary of the Treasury. The Secretary of the Treasury is authorized and directed to purchase any obligations of the Secretary issued under this section, and for such purposes is authorized to use as a public debt transaction the proceeds from the sale of any securities issued under chapter
31 of title
31, and the purposes for which such securities may be issued under such chapter are extended to include the purchases of the Secretary’s obligations hereunder.