The United States says North Korea may be hiding more nuclear sites with potential military uses after revealing its construction of a uranium enrichment facility.
U.S. envoy to the International Atomic Energy Agency Glyn Davies said Thursday there is a "clear likelihood" that North Korea has built other uranium enrichment-related facilities in its territory. He was speaking at a meeting of the IAEA's board of governors in Vienna.
Davies says Washington believes North Korea began pursuing uranium enrichment long before April 2009, when Pyongyang claims its latest project started.
North Korea said earlier this week that it has an enrichment facility with thousands of working centrifuges capable of producing fuel for a light water reactor currently under construction. Pyongyang said the facilities are designed for the peaceful generation of energy.
Enrichment also could give North Korea an alternative means to produce nuclear weapons in addition to its known plutonium-based weapons program.
IAEA chief Yukiya Amano expressed "great concern" Thursday about North Korea's new nuclear facilities.
His agency has been unable to verify North Korea's nuclear program since that state expelled U.N. inspectors last year and prevented the agency from engaging in full monitoring activities in 2002.
Pyongyang's nuclear revelations have contributed to a sense of crisis on the Korean peninsula following the North's deadly shelling of a South Korean island on November 23.
U.S. Secretary of State Hillary Clinton is due to meet her South Korean and Japanese counterparts in Washington on Monday to discuss a response to those developments.
The Chinese foreign ministry said Thursday it expects the three allies "to ease tensions and promote dialogue" on the Korean peninsula, "rather than heighten tensions and intensify confrontation." It says Beijing will watch the meeting "closely."
China has urged the United States, South Korea, Japan and Russia to send representatives to Beijing this month for emergency talks with North Korea aimed at easing regional tensions. The Chinese foreign ministry says Russia has expressed support for the idea.
The United States, South Korea and Japan have expressed reluctance to talk with North Korea at the present time, fearing that would reward Pyongyang for what they call provocative behavior. They say Pyongyang first must honor commitments made to regional powers to dismantle its nuclear weapons program.
The United States and Japan also are moving 40,000 troops into position for a major military exercise near the Korean peninsula beginning Friday. It follows a major U.S.-South Korean naval drill that ended Wednesday. Washington said that exercise was aimed at deterring North Korean attacks.