"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). [...] 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. Much of the current closeness between Seoul and Washington is due to President Lee. It is unclear how sustainable many of his policies will be, particularly into 2012, when South Koreans will elect a new president and a new legislature. Bilateral coordination will be particularly tested if South Korea's left-of-center groups, which bitterly oppose much of Lee's agenda, retake the presidency and/or the National Assembly. This report will be updated periodically."