North Korea tested atomic devices in 2006 and 2009 after receiving U.N. condemnation for launching long-range rockets.
The U.S. envoy on North Korean issues, Glyn Davies, urged Pyongyang not to explode an atomic device.
‘‘Whether North Korea tests or not, it’s up to North Korea. We hope they don’t do it. We call on them not to do it,’’ he told reporters in Seoul after meeting Thursday with South Korean officials. ‘‘It will be a mistake and a missed opportunity if they were to do it.’’
White House spokesman Jay Carney on Thursday said North Korea’s aggressive stance is unnecessary and warned against any further testing.
‘‘North Korea’s statement is needlessly provocative and a test would be a significant violation of United Nations Security Council resolutions,’’ he said. ‘‘Further provocation would only increase Pyongyang’s isolation, and its continued focus on its nuclear and missile program is doing nothing to help the North Korean people.’’
He said the recent U.N. resolution is a ‘‘strong message of the international community’s opposition to North Korean provocations and these tightened sanctions will impede the growth of weapons of mass destruction programs in North Korea and the United States will be taking additional steps in that regard.’’
Carney did not elaborate on what those steps might be.
In Beijing, chief North Korea ally China urged restraint, but declined to directly criticize the North’s actions.
‘‘To maintain peninsular peace and stability and achieve denuclearization is conducive to the interests of all sides.’’ Foreign Ministry spokesman Hong Lei told reporters Thursday.
‘‘The situation now is sensitive and complicated. We hope all sides can stay calm, be careful what they say and do, and avoid escalating tensions,’’ Hong said.
Associated Press writers Jean H. Lee in Seoul, Matthew Pennington in Washington and Christopher Bodeen in Beijing contributed to this report. Follow AP’s Korea bureau chief at www.twitter.com/newsjean.