U.N.: S. Korea Must Notify Us of Nuke Testing

South Korea (search) must not conduct any more nuclear experiments without notifying the United Nations, because any secret nuclear activity, however small, is a matter of "serious concern," the U.N. nuclear chief said Sunday.

The comments in Seoul by Mohamed ElBaradei (search), director of the International Atomic Energy Agency, came after North Korea warned that the South Korean experiments had disrupted a dialogue between the two Koreas.

The two Koreas have conducted a fitful reconciliation process since a 2000 summit between their leaders. Family reunions, Cabinet-level talks, and economic and cultural exchanges have been held, but their militaries remain on alert along the tense border and North Korea (search) was furious over the arrival of more than 400 North Korean defectors in Seoul in July.

The controversy over South Korea's experiments has also threatened to further disrupt troubled efforts to persuade North Korea to dismantle its suspected nuclear weapons programs.

North Korea has said the two South Korean experiments as well as what it calls the "hostile" policy of the United States have blocked progress in six-party talks on the North's nuclear activities. The six countries involved — the United States, the two Koreas, Japan, China and Russia — had planned to hold a round of negotiations in September, but the North spurned appeals to attend.

ElBaradei's visit to South Korea follows Seoul's recent admissions that it conducted a plutonium-based nuclear experiment more than 20 years ago and a uranium-enrichment experiment in 2000. South Korea says the experiments were purely research but has acknowledged it should have informed the IAEA.

"Any undeclared activities is a matter of serious concern for me," ElBaradei told reporters upon arrival. "However, as far as I know now, these have been small experiments. We just wanted to make sure these were experiments and that there were nothing more than these experiments ... (and that) these experiments will not be repeated again without being declared to the organization."

ElBaradei — who was in the country to take part in the Pugwash Conference on Science and World Affairs — said he believed a report on Seoul's nuclear activities would be ready for submission to the IAEA's board of governors by November.

Asked about the possibility of the issue being reported to the Security Council, which can impose punitive measures, he said such a decision "is far down the road."

"This is something for the board of governors members to decide," he said. "You cannot speculate on the issue before we have a comprehensive report on these experiments."

The IAEA has already sent inspectors here twice, and South Korean officials expect several more such visits.

Plutonium and enriched uranium are two key ingredients of nuclear weapons.