Senate Finance Committee Chairman Orrin Hatch, R-Utah, was quoted as saying he wants a "strong, enforceable, modernized" agreement, which some viewed as criticism of U.S. proposals to make NAFTA's dispute settlement mechanism nonbinding, something Canada has said it can't accept.
If the fifth round of talks next month in Mexico City is unproductive, alarm among members could grow, sparking Congress to assert its oversight authority.
Under NAFTA rules, a presidential notification of withdrawal is followed by a six-month waiting period. But even after that period, the benefits and obligations under the agreement wouldn't automatically disappear, according to trade attorneys.
Changing provisions related to customs, industry sectors, marking rules and other areas would require Congress to act because it passed legislation in 1993 to implement U.S. obligations and that package remains part of domestic law. Existing tariff rates would continue for one year.
That makes NAFTA different from the 2011 U.S.-Korea Free Trade Agreement, which says that if the parties decide not to participate anymore, virtually all laws associated with the agreement terminate, said Nicole Bivens Collinson, president of international trade and government relations at Sandler, Travis & Rosenberg.