"The United States and Mexico have a close and complex bilateral relationship. As neighbors and partners under the North American Free Trade Agreement (NAFTA), the United States and Mexico have extensive economic linkages, with bilateral trade valued at almost $400 billion in 2010. In recent years, security issues have dominated the bilateral relationship, and the United States is providing more than $1.6 billion worth of training and equipment to Mexico through the Mérida Initiative to support efforts against drug trafficking and organized crime. Immigration and border security have also returned to the forefront of the bilateral agenda since Arizona became the first state to enact a strict law against illegal immigration in April 2010."
CRS Report for Congress, RL32724
United States. Department of State, Foreign Press Centers, Bureau of Public Affairs: http://www.fpc.state.gov/