19 USC § 4516
Trade Representative authority
through Pub. L. 116-282, except Pub. L. 116-260
If a country (other than the United States) that has signed the USMCA does not enact implementing legislation, the Trade Representative is authorized to enter into negotiations with the other country that has signed the USMCA to consider how the applicable provisions of the USMCA can come into force with respect to the United States and that other country as promptly as possible.