Washington's key allies in East Asia have expressed concern at North Korea's announcement that it is bolstering its nuclear arsenal and urged the secretive nation to return to the negotiating table. South Korea voiced "serious concern" over a statement released by the north's Korean Central News Agency on Wednesday that quoted a foreign ministry spokesman as saying 8,000 fuel rods had been removed from its nuclear power plant in Yongbyon. The rods must be removed before they can be processed into other products, which could include weapons-grade plutonium. "North Korea should immediately halt actions that have a negative impact" on efforts to resume disarmament talks, CNN quoted South Korea's Foreign Ministry as saying. "We strongly urge North Korea to return to the six-party talks without delay." Japan joined the United States in saying that while they were concerned by developments, there was nothing new in the statement, which North Korea had made before to bolster its negotiating position. "We must work to show that North Korea will benefit the most from returning quickly to the six-nation talks and disposing of its nuclear program," Japanese Prime Minister Junichiro Koizumi said. U.S. officials said the statement seemed to be a re-release of an identical statement made two years ago. Urging a return to six-party talks, White House spokesman Scott McClellan said "North Korea's provocative comments only isolate it further from the rest of the international community." On Tuesday, China urged restraint but rejected using sanctions to prod North Korea to return to talks, with a spokesman saying Beijing's political and trade relations with its neighbor should be kept separate.