In order to carry out the provisions of sections 277 to 277d of this title, the President, or any Federal agency he may designate is authorized, (a) in his discretion, to enter into agreements with any one or more of said political subdivisions, in connection with the construction of any project or works provided for in paragraph (2) of section 277a and , under the terms of which agreements there shall be furnished to the United States, gratuitously, except for the examination and approval of titles, the lands or easements in lands necessary for the construction, operation, and maintenance in whole or in part of any such project or works, or for the assumption by one or more of any such political subdivisions making such agreement, of the operation and maintenance of such project or works in whole or in part upon the completion thereof: , That when an agreement is reached that necessary lands or easements shall be provided by any such political subdivision and for the future operation and maintenance by it of a project or works or a part thereof, in the discretion of the President the title to such lands and easements for such projects or works need not be required to be conveyed to the United States but may be required only to be vested in and remain in such political subdivision; (b) to acquire by purchase, exercise of the power of eminent domain, or by donation, any real or personal property which may be necessary; (c) to withdraw from sale, public entry or disposal of such public lands of the United States as he may find to be necessary and thereupon the Secretary of the Interior shall cause the lands so designated to be withdrawn from any public entry whatsoever, and from sale, disposal, location or settlement under the mining laws or any other law relating to the public domain and shall cause such withdrawal to appear upon the records in the appropriate land office having jurisdiction over such lands, and such lands may be used for carrying out the purposes of sections 277 to 277d of this title: , That any such withdrawal may subsequently be revoked by the President; and (d) to make or approve all necessary rules and regulations.section 277b of this title1Provided, howeverProvided