The head of the U.N. nuclear watchdog urged North Korea on Monday to return to the negotiating table to resolve the crisis surrounding the reclusive communist state's nuclear weapons program. "The earlier the parties go back to the negotiating table the better," International Atomic Energy Agency Director General Mohamed ElBaradei said on the sidelines of a global nuclear disarmament conference, Reuters said. Six-party talks involving the United States, North and South Korea, China, Japan and Russia on Pyongyang's nuclear program have been stalled for almost a year, and recent efforts to restart them have shown little progress. "There is no other solution except all of the parties put all their grievances together on the table and get a ... solution that addresses Korean security and economic needs and addresses this whole nuclear program," ElBaradei said. North Korea said explicitly for the first time in February that it had nuclear weapons, ratcheting up a crisis that began in October 2002 over what Washington said was its enrichment of uranium that could be used to make weapons. The IAEA chief has repeatedly referred to North Korea as the world's greatest nuclear proliferation threat. After kicking out U.N. inspectors, North Korea announced in early 2003 that it was withdrawing from the nuclear Non-Proliferation Treaty. The 188 signatories of the NPT are meeting this month to discuss ways of strengthening the 1970 pact aimed at stopping the spread of atomic weapons. Numerous foreign ministers who spoke at the opening session of the NPT review conference on Monday criticized North Korea and called on it to return to the six-party talks.