The second North Korean nuclear crisis, which was triggered by controversy over its alleged highly enriched uranium (HEU) program in October 2002, continues. Despite its roller-coaster trajectory, the Six Party Talks (6PT) process has paved the way for a peaceful diplomatic settlement of the nuclear standoff. Since the 6PT process has been primarily a negotiating arena for North Korea and the United States, through the mediation of China, room for South Korea's effective participation has been structurally limited. Nevertheless, the Roh Moo Hyun government played a significant role in suggesting innovative ideas, often defying the American stance to break impasses, and facilitating the overall process of negotiation through proactive diplomacy. This article unravels the Roh government's diplomatic role in the 6PT process by describing its initial perception of and reactions to U.S. positions on contentious issues such as the terms of engagement and exchange, and analyzing its role in linking the 6PT to a peace regime for Korea and a Northeast Asian regional security and peace mechanism. Key words: South Korea, multilateral security - East Asia, North Korea, nuclear weapons Introduction: The Second Nuclear Crisis Controversy over the highly enriched uranium (HEU) program in North Korea, which surfaced during U.S. special envoy James Kelly's visit to Pyongyang in October 2002, triggered the second nuclear crisis between North Korea and the United States. It was through the Six Party Talks (6PT) process that the nuclear stand-off began to show prospects for a peaceful settlement through diplomatic negotiations. But as with most negotiations with North Korea, the 6PT process, which has been underway since 2003, has been protracted, frustrating, and unpredictable. The first three rounds (2003-2004) of the 6PT did not produce any tangible outcome. The uncompromising attitudes of North Korea and the United States almost derailed the talks, particularly when the North declared its possession of nuclear weapons in February 2005 and refused to attend the talks indefinitely. A major breakthrough came during the fourth round with the adoption of the September 19, 2005 joint statement. However, the freeze of North Korean bank accounts at the Banco Delta Asia on September 20, 2005 and the North's subsequent provocative reactions- such as its missile tests on July 5 and underground nuclear test on October 9, 2006-eroded the very foundation of the 6PT. After a series of direct contacts between the United States and North Korea in early 2007, the 6PT were resumed and began to make concrete progress. The 6PT adopted the February 13 and the October 3 agreements for shutting down and sealing the nuclear facilities in Yongbyon, disabling those facilities, identifying nuclear materials and programs, and ultimately, verifiably dismantling all nuclear programs and materials, including nuclear weapons. The first phase of shutting down and sealing has been completed at this writing, and the second phase of disabling and declaration is also coming to an end as the United States removed North Korea from its list of terrorist-sponsoring states. The last phase of verifiable dismantling, however, is encountering formidable challenges. The 6PT process has been a negotiating arena for North Korea and the United States, through the mediation of China. Room for South Korea's participation has been structurally limited. But the South Korean government has played a significant role in suggesting innovative ideas, breaking occasional impasses, and facilitating the overall process of negotiation through proactive diplomacy. A growing body of literature on the second North Korean nuclear crisis and the 6PT process has failed to pay attention to the South Korean role, being preoccupied instead with analyzing negotiations between Pyongyang and Washington.1 This article fills the gap by delineating and explaining South Korea's diplomatic efforts in the 6PT process. …