The provisions of section 1336 of this title shall not apply to any article with respect to the importation of which into the United States a foreign-trade agreement has been concluded pursuant to this part or the Trade Expansion Act of 1962 [19 U.S.C. 1801 et seq.] or the Trade Act of 1974 [19 U.S.C. 2101 et seq.] or to any provision of any such agreement. The third paragraph of section 1311 of this title shall apply to any agreement concluded pursuant to this part or the Trade Expansion Act of 1962 or the Trade Act of 1974 to the extent only that such agreement assures to the United States a rate of duty on wheat flour produced in the United States which is preferential in respect to the lowest rate of duty imposed by the country with which such agreement has been concluded on like flour produced in any other country; and upon the withdrawal of wheat flour from bonded manufacturing warehouses for exportation to the country with which such agreement has been concluded, there shall be levied, collected, and paid on the imported wheat used, a duty equal to the amount of such assured preference.

Every foreign trade agreement concluded pursuant to this part shall be subject to termination, upon due notice to the foreign government concerned, at the end of not more than three years from the date on which the agreement comes into force, and, if not then terminated, shall be subject to termination there­after upon not more than six months’ notice.

The authority of the President to enter into foreign trade agreements under section 1351 of this title 1