The UN Security Council is planning an emergency meeting to discuss North Korea's hydrogen bomb claims
Speaking to Reuters on condition of anonymity, several diplomats said the meeting was scheduled to take place at 11 a.m. ET (1600 GMT). The diplomats said the meeting would likely be held behind closed doors.
"The United States and Japan have requested emergency Security Council consultations for (Wednesday) morning regarding North Korea's alleged nuclear test," Hagar Chemali, spokeswoman for the U.S. mission, said in a statement.
"While we cannot confirm at this time that a test was carried out, we condemn any violation of UNSC (U.N. Security Council) Resolutions and again call on North Korea to abide by its international obligations and commitments," she added.
North Korea said it had successfully conducted a test of a miniaturized hydrogen nuclear device on Wednesday morning, marking a significant advance in the isolated state's strike capabilities and ringing alarm bells in Japan and South Korea.
"We plan to work with other countries so that a resolution with strong content can be adopted at the U.N. Security Council as swiftly as possible," Japanese Foreign Minister Fumio Kishida told reporters.
It was not immediately clear what action, if any, the 15-nation council was planning to take in response to the North Korean statement that it had conducted a fourth nuclear test.
Pyongyang has been under U.N. Security Council sanctions due to its nuclear weapons program since it first tested an atomic device in 2006.
One Western diplomat said that if the latest North Korean nuclear test was confirmed, council members would seek to expand existing U.N. sanctions against Pyongyang.
(Additional reporting by Michelle Nichols; Editing by Richard Pullin, Robert Birsel and Chizu Nomiyama)