The secretive North Korean regime has said it is planning a nuclear test and more long-range rocket launches, aimed at what it calls its "sworn enemy", the United States.
The move, which comes in defiance of a resolution issued by the UN on Tuesday, is likely to once again raise tensions in the region over the North Korean missile program.
On Tuesday the UN Security Council condemned North Korea for test-firing a missile in December and tightened existing sanctions on the regime.
The National Defence Commission of Korea responded by saying the new nuclear test would be part of its action against the "sworn enemy of the Korean people".
The regime has also said it plans to press ahead with the ongoing testing of long-range missiles.
The declaration by the National Defence Commission, said: "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."
"Settling accounts with the US needs to be done with force, not with words, as it regards jungle law as the rule of its survival," the statement continued.
In the statement the National Defence Commission describes the UN Security Council as "a marionette of the US".
The response shows a marked escalation in tensions between Kim Jong-un's regime and the West.
The new UN resolution and sanctions follow the launch last month of a long-range rocket. The North Korean's insists the launch was part of its peaceful space programme, but the US and its allies believe the purpose was to test its ballistic missile technology.
Today's statement did not clarify when the new nuclear test will take place, though analysts are suggesting it could happen in mid-February.
The commission statement, carried by the official Korean Central News Agency did not give any explanation of the meaning of "high level".
Washington urged North Korea not to proceed with a third test just as the North's statement was published.
"Whether North Korea tests or not is up to North Korea," Glyn Davies, the top U.S. envoy for North Korean diplomacy, said in the South Korean capital of Seoul.
"We hope they don't do it. We call on them not to do it," Davies said after a meeting with South Korean officials. "This is not a moment to increase tensions on the Korean peninsula."
The North was banned from developing missile and nuclear technology under sanctions dating from its 2006 and 2009 nuclear tests.
A South Korean military official said the concern now is that Pyongyang could undertake a third nuclear test using highly enriched uranium for the first time, opening a second path to a bomb.
North Korea's 2006 nuclear test using plutonium produced a puny yield equivalent to one kiloton of TNT - compared with 13-18 kilotons for the Hiroshima bomb - and US intelligence estimates put the 2009 test's yield at roughly two kilotons
North Korea is estimated to have enough fissile material for about a dozen plutonium warheads, although estimates vary, and intelligence reports suggest that it has been enriching uranium to supplement that stock and give it a second path to the bomb.
According to estimates from the Institute for Science and International Security from late 2012, North Korea could have enough weapons grade uranium for 21-32 nuclear weapons by 2016 if it used one centrifuge at its Yongbyon nuclear plant to enrich uranium to weapons grade.