Leaders from the 39 member states of the Asia-Europe Meeting (ASEM) that closed after a two-day run here reiterated the importance of diplomacy in dealing with the nuclear issue, cautioning against any action that might aggravate the situation. In the chairman's statement adopted at the closing session, the leaders also renewed their determination to further cooperate in dealing with global challenges, such as new security threats including terrorism and the side-effects of globalization. ``They emphasized that the denuclearization of the Korean Peninsula is essential in maintaining peace and stability in Northeast Asia, and voiced support for the peaceful resolution of the North Korean nuclear issue through dialogue,'' it said. The statement added that the leaders reaffirmed their support for the Sept. 19, 2005 joint statement adopted in the six-party talks in Beijing, while expressing ``serious concern'' over the recent test-firing of missiles by North Korea. ``They also stressed that any action that might further aggravate the situation should be refrained from, and urged North Korea to return immediately to the six-party talks without precondition,'' it said. President Roh Moo-hyun, who held a joint press conference with other leaders including the Finnish prime minister and Indonesian president, thanked them for supporting Seoul's efforts to end the nuclear issue in a peaceful manner. ``I offer my sincere gratitude to the Asian and European heads of state for lending support in unison for South Korea's endeavors for the improvement of inter-Korean relations and the peaceful resolution of the nuclear issue,'' he said. Roh is scheduled to hold a summit with U.S. President George W. Bush in Washington on Sept. 14, in which the North Korean issues will be one of the top agenda items. Seoul favors a peaceful resolution to the issue despite Pyongyang's acts of raising tension, including missile tests in early July. But Washington is said to be considering additional sanctions, such as restrictions on trade and investments. The Roh-Bush summit, the sixth of its kind since early 2003, comes at a time when the Americans observe the fifth anniversary of the Sept. 11 terror attacks. Roh is scheduled to arrive in Washington on Sept. 12. Roh has been trying to take the initiative at the ASEM forum ahead of talks with Bush, as the upcoming summit is expected to be a watershed for the resumption of the six-way talks, deadlocked for months. As part of such efforts, he played down North Korea's missile tests on July 4, describing them as an action motivated by political purposes rather than a real threat, a comment that could hint at his approach in his talks with Bush. Beside the ASEM forum and the summit with Bush, Roh is also scheduled to make a working visit to China for talks with President Hu Jintao in mid-October, making this autumn a season of diplomacy for the South Korean president. Roh held a flurry of summits with European leaders last week when he visited Greece, Romania and Finland. On the sidelines of the ASEM forum, he also met with French, Danish and Slovakian leaders. ``In his two-week European and American tour, the president has been trying to strengthen ties with the countries he is visiting while also focusing on the North Korean nuclear issue,'' a presidential aide accompanying Roh said. By Ryu Jin Korea Times Correspondent