Pyongyang, through its official Korean Central News Agency, issued a statement suggesting it was preparing a third nuclear test as part of "the next phase of the anti-U.S. struggle."
In December, North Korea, after a failed attempt in April, launched a long-range rocket to put a satellite into orbit. Launches in 2006 and 2009 coincided with the testing of nuclear devices.
Blog 38 North from the U.S.-Korea Institute at Johns Hopkins University states that satellite imagery of the Punggye-ri Nuclear Test Facility has revealed activity thought to indicate a nuclear detonation may be imminent.
North Korea's statement followed a decision by the U.N. Security Council to censure Pyongyang for the December launch.
China, a party to stalled nuclear negotiations, expressed concern over North Korea's recent rhetoric. An editorial published Friday in state-run news agency The Global Times warns there would be consequences if North Korea carries out another nuclear test.
"If North Korea engages in further nuclear tests, China will not hesitate to reduce its assistance to North Korea," the editorial stated. "If the United States, Japan and South Korea promote extreme U.N. sanctions on North Korea, China will resolutely stop them and force them to amend these draft resolutions."
Washington cut off promised food assistance to North Korea last year in response to the failed April launch.