(Adds background, looming NAFTA re-negotiation)
MEXICO CITY, May 8 (Reuters) - Mexico's auto exports rose 16.1 percent in April compared was the same month a year earlier, and output was up 3.2 percent, the Mexican Auto Industry Association (AMIA) said on Monday.
Mexico exported 228,810 vehicles and produced 278,173 vehicles in April, AMIA said.
Auto exports to the United States, Mexico's top trading partner, were up nearly 20 percent to reach 179,958 units.
Mexico accounts for about a fifth of all vehicle production in North America.
Total auto exports during the first four months of the year were up nearly 15 percent compared with the same four-month period last year, reaching 978,972 units.
Mexican authorities are bracing for a looming re-negotiation of the North American Free Trade Agreement (NAFTA) with the United States and Canada, as U.S. President Donald Trump has insisted that a new pact must be more "fair" to American workers and companies.
Mexico's booming auto sector has been a clear beneficiary of NAFTA as a wide range of international automakers have made Latin America's second biggest economy a key export hub, attracted by cheap labor costs and free trade accords with dozens of nations. (Reporting by Anthony Esposito; Editing by W Simon and Tom Brown)