"The United States and Mexico have a special relationship as neighbors and partners under the North American Free Trade Agreement (NAFTA). Although relations with Mexico are generally friendly, the enactment of border fence legislation in October 2006 has caused some tension in the bilateral relationship. […] Migration and border security concerns have dominated the bilateral relationship in recent years. Immigration reform legislation has been introduced in both the House and Senate. The Senate began debate on the Comprehensive Immigration Reform Act of 2007 (S. 1348) in May 2007. In September 2006, Congress approved the Secure Fence Act of 2006 (P.L. 109-367) to authorize the construction of a border fence and other barriers along 700 miles of the U.S.-Mexico border. In September 2006, Congress also approved initial funding for fence construction, $1.2 billion, through the FY2007 Department of Homeland Security Appropriations Act. Both the House and Senate approved immigration reform measures (H.R. 4437 and S. 2611, respectively) but did not meet in conference to resolve differences. Principal sticking points include the House provision that would criminalize unlawful presence and Senate provisions to adjust the status of certain illegal immigrants. Bush Administration officials regularly praised Mexico's counternarcotics efforts under former President Vicente Fox and anticipate continued strong relations under President-elect Felipe Calderón. Mexico is the leading transit country for cocaine, a leading supplier of methamphetamine, and the leading foreign supplier of marijuana to the United States. The USA Patriot Act Improvement and Reauthorization Act of 2005 (P.L. 109-177), enacted in March 2006, includes provisions to combat methamphetamine smuggling from Mexico."
CRS Report for Congress, RL32724