WASHINGTON North Korea had advised the U.S. State Department of its intention to test a nuclear device prior to Tuesday's underground explosion, but had not said when it would conduct the test, department spokeswoman Victoria Nuland said.
"The DPRK did inform us at the State Department of their intention to conduct a nuclear test, without citing any specific timing," she told reporters, using North Korea's formal name, the Democratic People's Republic of Korea.
Nuland said the notice came through the "usual channel" but declined to say exactly when Washington received the notification. This usually refers to an office in New York where phone messages and faxes are exchanged between the two countries, which do not have diplomatic relations.
Secretary of State John Kerry had telephone conversations with his counterparts in Japan and South Korea, both U.S. allies, and with North Korea's ally, China, she said.
Kerry was still trying to reach Russian Foreign Minister Sergei Lavrov, who was traveling in South Africa, added Nuland.
(Reporting by Paul Eckert; Editing by Sandra Maler)