The source of all commodities financed with Federal program funds appropriated under the Foreign Assistance Act of 1961, as amended, shall be Code 937 (unless Code 935 or 110 are designated in the implementing instrument). Procurements of agricultural commodities, motor vehicles, and pharmaceuticals must also comply with the special procurement rules in § 228.19. Recipients and contractors are prohibited from engaging suppliers of commodities in an authorized country to import commodities from a country outside of the authorized principal geographic codes for the purposes of circumventing the requirements of this section. Any violation of the prohibition in the preceding sentence will result in the disallowance by USAID of the cost of the procurement of the subject commodity.