From the introduction to NAFTA Renegotiation and the Proposed United States-Mexico-Canada Agreement (USMCA) (R44981, Feb. 26, 2019):
The 116th Congress faces policy issues related to the Trump Administration’s renegotiation of the North American Free Trade Agreement (NAFTA) and the proposed United States-Mexico-Canada Agreement (USMCA). On May 18, 2017, the Trump Administration sent a 90-day notification to Congress of its intent to begin talks with Canada and Mexico to renegotiate and modernize NAFTA, as required by the 2015 Trade Promotion Authority (TPA). Talks officially began on August 16, 2017. Negotiations were concluded on September 30, 2018. The proposed USMCA was signed on November 30, 2018. The agreement must be approved by Congress and ratified by the governments of Mexico and Canada before it can enter into force.