The economic and trade relationship with Mexico is of interest to U.S. policymakers because of Mexico's proximity to the United States, the extensive trade and investment relationship under the North American Free Trade Agreement (NAFTA), the conclusion of the NAFTA renegotiations and the proposed U.S.-Mexico-Canada Agreement (USMCA), and the strong cultural and economic ties that connect the two countries. Also, it is of national interest for the United States to have a prosperous and democratic Mexico as a neighboring country. Mexico is the United States' third-largest trading partner, while the United States is, by far, Mexico's largest trading partner. Mexico ranks third as a source of U.S. imports, after China and Canada, and second, after Canada, as an export market for U.S. goods and services. The United States is the largest source of foreign direct investment (FDI) in Mexico. Most studies show that the net economic effects of NAFTA, which entered into force in 1994, on both the United States and Mexico have been small but positive, though there have been adjustment costs to some sectors within both countries. Much of the bilateral trade between the United States and Mexico occurs in the context of supply chains as manufacturers in each country work together to create goods. The expansion of trade since NAFTA has resulted in the creation of vertical supply relationships, especially along the U.S.-Mexico border. The flow of intermediate inputs produced in the United States and exported to Mexico and the return flow of finished products greatly increased the importance of the U.S.-Mexico border region as a production site. U.S. manufacturing industries, including automotive, electronics, appliances, and machinery, all rely on the assistance of Mexican manufacturers. Congress faces numerous issues related to U.S.-Mexico trade and investment relations. The United States, Mexico, and Canada signed the proposed USMCA on November 30, 2018, which would have to be approved by Congress and ratified by Mexico and Canada before entering into force. A few days after signing the agreement, President Donald J. Trump stated to reporters that he intends to notify Mexico and Canada of his intention to withdraw from NAFTA with a six month notice. Congress may consider policy issues and economic effects of the proposed USMCA, economic and political ramifications of possibly withdrawing from NAFTA, and the potential strategic implications of Mexico's new President Andrés Manuel López Obrador, who entered into office on December 1, 2018. Congress may also examine the congressional role in a possible withdrawal from NAFTA; evaluate the effects of U.S. tariffs on aluminum and steel imports from Mexico and Mexico's retaliatory tariffs on certain U.S. exports; and address issues related to the U.S. withdrawal from the proposed Trans-Pacific Partnership (TPP) free trade agreement among the United States, Canada, Mexico, and nine other countries, and the Comprehensive and Progressive Trans-Pacific Partnership (CPTPP), which will enact much of the proposed TPP without the participation of the United States. The CPTPP is set to take effect for Mexico and five other countries on December 30, 2018. Some observers contend that the withdrawal from TPP could damage U.S. competitiveness and economic leadership in the region, while others see the withdrawal as a way to prevent lower-cost imports and potential job losses. Congress also may maintain an active interest in ongoing bilateral efforts to promote economic competitiveness, increase regulatory cooperation, and pursue energy integration. Under the U.S.Mexico High Level Economic Dialogue (HLED), which was first launched in September 2013, the United States and Mexico are striving to advance economic and commercial priorities through annual meetings at the Cabinet level - and other initiatives - that also include leaders from the public and private sectors.