SEOGIPWO - South Korean and Southeast Asian leaders will describe North Korea's nuclear test as a threat to regional peace during a summit starting Monday, Seoul's presidential office said.

President Lee Myung-Bak and his counterparts from the Association of Southeast Asian Nations (ASEAN) will describe the test as "a provocative act" in violation of UN resolutions and agreements at six-party nuclear disarmament talks, the office said in a press release.

They will say that the test "seriously undermines peace and stability not only in East Asia but also in the whole world," according to the press release, issued before the two-day summit was scheduled to begin Monday afternoon.

Thai Prime Minister Abhisit Vejjajiva said a formal statement would come at the end of the meeting on the southern resort island of Jeju.

It will "reaffirm our stance and desire for peace and stability in the region," Abhisit was quoted by Yonhap news agency as saying, adding senior officials from both sides were working on the text.

North Korea on May 25 tested a nuclear bomb estimated to be around four times more powerful than its first in 2006, sparking worldwide protests.

Leading members of the UN Security Council are negotiating a new resolution which could impose fresh sanctions.