In the case of Insular public works involving an expenditure of less than three thousand pesos, it shall be discretionary with the Director of Public Works either to proceed with the work himself or to let the contract to the lowest bidder after such publi cation and notice as shall be deemed appropriate or as may be, by regulation, prescribed. [584-5, 6; 888-4; 1401-5; 1752-2; 2019.] SECTION  1143 . Authority to Reject Bids . — When such course appears best to subserve the interest of the Government, the Director of Public Works may reject any or all bids for any contract subject to his award; and when all bids are rejected he may proceed  to advertise anew, or with the approval of the Secretary of Commerce and Police, he may himself proceed to execute the work. [584-6.] SECTION  1144 . Letting of Contract for Provincial Works.  — Except in the case of work upon roads or trails, every provincial public work of construction or repair involving an estimated expenditure of three thousand pesos or more shall be let to the lowest  responsible bidder, after public advertisement for not less than ten days in a paper of general circulation in the province, if such there be, and by notice posted for not less than ten days at the main entrance of the provincial building; but nothing here in shall be construed to prevent the giving of such further notice or making such further publication as will secure ample publicity for all invitations for bids. Provincial work not within the purview of the preceding paragraph may be prosecuted upon provincial account or may be let without advertisement, subject to the regulations of the Bureau of Public Works. The district engineer shall perform the duties incident to advertising for bids for provincial public works, and the letting of contracts therefor; and with the approval of the provincial board, he may reject any or all bids received, in which case he may  advertise anew or, with the approval of the board, may proceed with the execution of the work upon provincial account. [1401-5; 1752-2.] SECTION  1145 . Execution of Contracts for Public Works . — Contracts awarded by the Director of Public Works for the construction or repair of public works and improvements of any kind shall be executed on behalf of the Government by said Director, with the  approval of the Secretary of Commerce and Police. Copyright 2012 CD Technologies Asia, Inc. and Accesslaw, Inc. Philippine Law Encyclopedia 2011 343