"For over 50 years, U.S. trade officials have negotiated multilateral trade agreements to achieve lower trade barriers and rules to cover international trade. During the 108th Congress, U.S. officials negotiated and Congress approved four bilateral free-trade agreements with Australia, Chile, Morocco, and Singapore. The Bush Administration is making bilateral and regional free-trade agreements more important elements of its trade policy. The multilateral arena is no longer the only means, or perhaps even the principal means, by which the United States is pursuing liberalized trade. Trade agreements are negotiated by the executive branch, although Congress has the ultimate Constitutional authority to regulate interstate and foreign commerce. Trade promotion authority (TPA) requires that the President consult with and advise Congress throughout the negotiating process. After the executive branch signs an agreement, Congress may consider implementing legislation if any statutory changes are required under the agreement. There is no deadline for submission of the legislation, but once a bill is submitted, TPA requires a final vote within 90 legislative days."
CRS Report for Congress, RL33463