North Korea conducted a new "crucial" test at the Sohay launch site to launch satellites to bolster its capabilities in strategic nuclear deterrence, as nuclear negotiations between Pyongyang and Washington remain stalled, with the deadline approaching.

"The successes in the research field will be applied to improve North Korea's credible strategic nuclear deterrence," the official news agency quoted a spokesman for the "North Korean National Academy of Defense Sciences" as saying.

The statement did not provide additional details about the test, and the experiment is the second of its kind in the facility within a week.

The agency reported last Sunday that North Korea had conducted a "very important" test on December 7 at the Sohay satellite launch site, which is conducting missile tests, which US officials once said North Korea had promised to shut down.

That report described the experiment as "a successful test of great importance," and South Korean Defense Minister Young Kyung Do said it was a test drive.

The Sohay coastal facility in northwestern North Korea is ostensibly designed to put satellites into orbit, but Pyongyang launched several missiles from the site in condemned operations from the United States and others, as tests of long-range ballistic missiles were being concealed.

News of the experiments comes before it expires at the end of the year, a deadline granted by Pyongyang to Washington to back down from its insistence on unilateral nuclear disarmament.

North Korea has warned it could take a "new path" as talks with the United States falter.

The top US envoy to North Korea is scheduled to arrive in Seoul tomorrow, Sunday, for meetings with South Korean officials.

On Friday, US Defense Secretary Mark Asper said the United States would "test soon" the possibility of returning North Korea to the negotiating table.

"They are still conducting exercises, conducting short-range ballistic missile tests that concern us," he added.

Analysts said such tests could help North Korea manufacture more reliable intercontinental ballistic missiles.