technology. There had also been strong anti-American sentiment during certain periods, which has largely moderated in the modern day. Since the late 1980s, the country has instead sought to establish an American partnership, which has made the Seoul–Washington relationship subject to severe strains. Trade had become a serious source of friction between the two countries. In 1989, the United States was South Korea's largest and most important trading partner and South Korea was the seventh-largest market for United States goods and the second largest market for its agricultural products. From Roh Tae-woo's administration to Roh Moo Hyun's administration, South Korea sought to establish a U.S. partnership, which has made the Seoul–Washington relationship subject to some strains. In 2007, a free trade agreement known as the Republic of Korea-United States Free Trade Agreement (KORUS FTA) was reportedly signed between South Korea and the United States, but its formal implementation has been repeatedly delayed, pending further approval by the legislative bodies of the two countries. The relations between the United States and South Korea have greatly strengthened under the Lee Myung-bak administration. At the 2009 G-20 London summit, U.S. President Barack Obama called South Korea "one of America's closest allies and greatest friends." However, some anti-American sentiment in South Korea still exists; the United States' alleged role in the May 1980 Gwangju uprising was a pressing South Korean political issue of the 1980s. Even after a decade, some Gwangju citizens and other South Koreans still blamed the United States for its perceived involvement in the bloody uprising. In 2008, the protests against U.S. beef was a center of a major controversy that year. In a June 2010 open letter from President of South Korea Lee Myung-bak published in the Los Angeles Times, he expressed gratitude for the 37,000 Americans who were killed in the Korean War defending South Korea, saying that they fought for the freedom of South Koreans they did not even know. He stated that thanks to their sacrifices, the peace and democracy of the South Korean state was protected. The U.S. states that "The Alliance is adapting to changes in the 21st Century security environment. We will maintain a robust defense posture, backed by allied capabilities which support both nations' security interests We will continue to deepen our strong bilateral economic, trade and investment relations In the Asia-Pacific region we will work jointly with regional institutions and partners to