(a) Motor vehicles to be manufactured in North America.--All government agencies shall procure only motor vehicles which are manufactured in North America. A motor vehicle is manufactured in North America if a substantial majority of the principal components are assembled into the final product in an assembly plant in North America. Contract documents for the procurement of motor vehicles shall contain a provision that the vehicles procured by the government agency shall be manufactured in North America.

(b) Exception.--This section shall not apply where the head of the government agency states in writing that it is inconsistent with the public interest or that the cost is unreasonable.