"We do not hide that the various satellites and long-range rockets we will continue to launch, as well as the high-level nuclear test we will proceed with, are aimed at our arch-enemy the United States," the National Defence Commission said.
The mention of the test, which would mark the North's third detonation of a nuclear device, came towards the end of a commission statement carried by the official Korean Central News Agency.
The statement was entitled: "Enter all-out confrontation to safeguard the sovereignty of the nation and people."
It gave no indication of when the test might be carried out, or explain the meaning of "high-level". The North's two previous nuclear tests were held in 2006 and 2009.
Much of the statement was devoted to condemning Tuesday's announcement by the UN Security Council of expanded sanctions against Pyongyang in response to its long-range rocket launch last month.
"We absolutely refute all the illegal and outlawed resolutions adopted by the Security Council," the commission said.
Tuesday's resolution, proposed by the United States, was adopted unanimously by the 15-nation council, including the North's sole major ally China.
North Korea's foreign ministry had denounced the move on Wednesday, when it also gave the first hint that Pyongyang would react with a nuclear test, saying the country would take "physical actions" to boost its nuclear deterrent.
South Korea's Yonhap news agency, citing a South Korean intelligence source, reported that Pyongyang had finished technical preparations and could conduct an atomic test within days of a decision by leader Kim Jong-Un.
Last month, a US think-tank reached a similar conclusion based on satellite photos, suggesting the North had repaired rain damage at its nuclear test site and could conduct a detonation at two weeks' notice.
China, which had sought to shield North Korea from harsher sanctions sought by the United States and its allies, appealed on Wednesday for restraint and diplomatic efforts to avoid a dangerous escalation of tensions.
"The DPRK's (North Korea's) satellite launch as well as speculation of a nuclear test highlight the urgency and importance of settling relevant issues on the Korean peninsula," foreign ministry spokesman Hong Lei told reporters.
"We hope all parties will bear in mind peace and stability of the Korean peninsula, exercise calmness and restraint and avoid actions that might escalate tension."
AFP
