If the United States does not, at the expiration of the existing license, exercise its right to take over, maintain, and operate any project or projects of the licensee, as provided in
section 807 of this title, the commission is authorized to issue a new license to the existing licensee upon such terms and conditions as may be authorized or required under the then existing laws and regulations, or to issue a new license under said terms and conditions to a new licensee, which license may cover any project or projects covered by the existing license, and shall be issued on the condition that the new licensee shall, before taking possession of such project or projects, pay such amount, and assume
such contracts as the United States is required to do in the manner specified in