; or (2) a tariff or nontariff barrier or policy or practice of such government with respect to United States exports of any product has been imposed or discovered, the United States Trade Representative shall withdraw any modification of any duty that reduced or eliminated the bound or applied rate of duty on any product that has the same physical characteristics and uses as a product described in paragraph (1) or (2) until such time as the Department of Commerce submits to Congress a certification that the foreign government has reduced or eliminated the tariff or nontariff barrier or policy or practice. (b) Investigation (1) In general The Department of Commerce shall initiate an investigation if an interested party files a petition with the Department of Commerce which alleges the elements necessary for the withdrawal of the modification of an existing duty under subsection (a), and which is accompanied by information reasonably available to the petitioner supporting such allegations. (2) Interested party defined For purposes of paragraph (1), the term interested party means— (A) a manufacturer, producer, or wholesaler in the United States of a domestic product that has the same physical characteristics and uses as the product for which a modification of an existing duty is sought; (B) a certified union or recognized union or group of workers engaged in the manufacture, production, or wholesale in the United States of a domestic product that has the same physical characteristics and uses as the product for which a modification of an existing duty is sought; (C) a trade or business association a majority of whose members manufacture, produce, or wholesale in the United States a domestic product that has the same physical characteristics and uses as the product for which a modification of an existing duty is sought