South Korean President Lee Myung-bak on Thursday highlighted the significance of the country\'s free-trade agreement with the United States and his commitment to end North Korea\'s nuclear programs as he delivered a rare address to a joint session of Congress. The speech, which came hours after Lee\'s summit with U.S. President Barack Obama, was organized to mark the trade deal\'s passage in Congress a day earlier. Lee was the first South Korean leader to speak at a joint Congressional session in 13 years after a 1998 speech by late former President Kim Dae-jung. Lee said the pact is another milestone in relations between the two countries after a 1953 defense agreement forged at the end of the 1950-53 Korean War, in which the U.S. fought alongside the South against invading troops from the communist North. \"The Korea-U.S. free-trade agreement was ratified by this Congress here last night,\" Lee said. \"Here, where the Mutual Defense Treaty was signed by Korea and the United States in 1953, a new chapter in our relationship has opened. Our relationship has become stronger.\" \"This agreement is a major step toward future growth and job creation. It is a win for our corporations. It is a win for our workers. It is a win for small businesses. And it is a win for all the innovators on both sides of the Pacific,\" he said. The address was interrupted 45 times for applause and standing ovations. One of the biggest standing ovations came when Lee singled out the names of congressmen who served in the Korean War -- Reps. John Conyers, Charles Rangel, Sam Jonson and Howard Coble -- and expressed thanks for them. Lee also underscored his commitment to a nuclear-free North Korea and to eventual unification. \"I recognize the reality that Korea has been split in two. But I will never accept it as a permanent condition,\" he said. \"We are one people. In both Koreas, there are families who have never spoken to their loved ones for more than half a century. My hope is that these people and all 70 million Koreans will enjoy real happiness, real peace.\" Lee also said that a unified Korea will be \"a friend to all and a threat to none,\" he said, stressing the need for a a nuclear-free Korean Peninsula. \"North Korea must give up their nuclear ambitions,\" he said. Lee also said that Seoul and Washington stand united in dealing with the North. \"We are in full agreement that we must also pursue dialogue with North Korea. However, we must also maintain our principled approach. A North Korea policy that is firmly rooted upon such principles is the key that will allow us to ultimately and fundamentally resolve the issue.\" Despite threats and provocations by the North, Lee has stuck to his long-standing policy that the communist nation should first give up nuclear programs if any large-scale aid and inter-Korean cooperation can resume. During the Congressional speech, Lee also called for closer cooperation with the U.S. in renewable energy and environment-friendly \"green growth\" industries.