"Since late 2008, relations between the United States and South Korea (known officially as the Republic of Korea, or ROK) have been arguably at their best state in decades. By the middle of 2010, in the view of many in the Obama Administration, South Korea had emerged as the United States' closest ally in East Asia. Of all the issues on the bilateral agenda, Congress has the most direct role to play in the proposed Korea-U.S. Free Trade Agreement (KORUS FTA). Congressional approval is necessary for the agreement to go into effect. On October 3, 2011, President Obama submitted draft legislation (H.R. 3080/S. 1642) to implement the FTA. This moves has been expected since early December 2010, when the two sides announced they had agreed on modifications to the original agreement, which was signed in 2007. South Korea accepted a range of U.S. demands designed to help the U.S. auto industry and received some concessions in return. In the United States, the supplementary deal appears to have changed the minds of many groups and Members of Congress who previously had opposed the FTA. If Congress approves the agreement, it would be the United States' second-largest FTA, after the North American Free Trade Agreement (NAFTA). [...] The United States maintains about 28,500 troops in the ROK. Since 2009, the two sides have accelerated steps to transform the U.S.-ROK alliance's primary purpose from one of defending against a North Korean attack to a regional and even global partnership. Washington and Seoul have announced a 'Strategic Alliance 2015' plan to relocate U.S. troops on the Peninsula and boost ROK defense capabilities. Some Members of Congress have criticized the relocation plans."
CRS Report for Congress, R41481
U.S. Dept. of State, Foreign Press Centers: http://fpc.state.gov/