U.S. Defense Secretary Robert Gates says the United States will not accept a nuclear-armed North Korea.
Meeting with Asian defense ministers in Singapore Saturday, Gates said painful sanctions against North Korea may be the only way to end its nuclear program peacefully.
He said Washington will not stand by as Pyongyang builds the capability to destroy targets in Asia or the United States.
A top Chinese military official at the conference called for calm. Ma Xiaotian (deputy chief of the general staff of the People's Liberation Army) told the delegates that the Korean peninsula should move towards denuclearization.
Meantime, Moscow says Russian President Dmitry Medvedev and Japanese Prime Minister Taro Aso both support the need for a strong response to North Korea's recent nuclear tests. A Kremlin statement says the two leaders spoke by telephone Saturday, and agreed to work together on measures to be included in a new U.N. Security Council resolution.
The U.N. Security Council is considering possible new sanctions against Pyongyang following its recent tests of short-range missiles and its claims to have carried out an underground atomic explosion.
North Korea has threatened to take retaliatory action if the United Nations imposes sanctions.
U.S. officials said Friday there are new signs that North Korea may be planning more long-range missile launches.
The United States says it is sending its North Korea envoy, Stephen Bosworth, to Asia next week along with Deputy Secretary of State James Steinberg for talks on how to respond to North Korea's missile tests.
Also Friday, U.S. officials said an initial U.S. air sampling from near the underground North Korean test site was inconclusive. North Korea said it carried out the test on Monday, and seismometers recorded shock waves that are consistent with an atomic explosion.
Pyongyang announced this week it is no longer bound by the 1953 armistice that ended fighting in the Korean War. And it warned South Korea it would take military action if Seoul and the United States make any move to intercept North Korean vessels under a U.S.-led effort (Proliferation Security Initiative) to restrict weapons of mass destruction.
The move prompted South Korean and U.S. forces on the Korean peninsula to raise their alert level to its highest level since 2006, when the North conducted its first nuclear test.