The chief of the U.N. nuclear watchdog agency, Mohamed ElBaradei, has again called for North Korea to return to the Non-Proliferation Treaty it abandoned in 2003. Mr. ElBaradei also criticized the U.N. Security Council for failing to take action against the communist state, and said an investigation into secret nuclear experiments by South Korea is continuing.
The director-general of the International Atomic Energy Agency was addressing the Pugwash anti-nuclear weapons conference in Seoul.
He said that by failing to take action against North Korea for violating international nuclear agreements, the Security Council had sent a signal to rogue nations that they are free to acquire nuclear capability without worrying about the consequences.
Mr. ElBaradei said this set the "worst precedent of all."
John Simpson, the director of the Mountbatten Centre for International Studies in Southampton, England, says he is not surprised to hear Mr. ElBaradei criticize the Security Council.
"Mr. ElBaradei is really the only United Nations civil servant who is really in a position to offer authoritative perspective upon how the nuclear non-proliferation regime could evolve. This is a role which he increasingly has sort of taken upon himself, " he said.
Mr. ElBaradei told reporters the IAEA is continuing to investigate recently-revealed nuclear experiments conducted in secret by South Korean government scientists.
"We are going through the process until we understand fully the extent of these experiments," said Mr. ElBaradei. "If we need one team or two we will dispatch them until we bring the issue to a closure."
Pyongyang has said it will not return to six-party negotiations on its own nuclear program until the South Korean experiments are fully investigated.
But Mr. ElBaradei said the "laboratory" experiments conducted by South Korea were very different from North Korea's "fully operating" nuclear reprocessing plant, and he said the two situations could not be compared.
He called for Pyongyang to return to the obligations of the international nuclear Non-Proliferation Treaty, which include allowing U.N. monitors into the country.
North Korea withdrew from the treaty in 2003 - an action Mr. ElBaradei says brought "little or no response" from the Security Council.
Noting the success achieved in diplomacy and verification with Iran and Libya, he expressed the hope that the six-party talks would resume and yield results.
Three rounds of talks - involving both Koreas, the United States, China, Japan, and Russia - have failed to achieve a breakthrough. A fourth round of talks set for last month was postponed after North Korea said it would not attend.
Tension has been high for two years, since Washington accused Pyongyang of having a secret uranium-based nuclear weapons program. North Korea has denied running a program based on enriched uranium, but admits it has restarted a separate plutonium-based operation.