North Korea said Thursday that it would build a nuclear missile capable of striking the United States after the UN Security Council tightened sanctions against the country.

In what The New York Times labeled as Kim Jong Un's "boldest challenge" to the Washington yet, Pyongyang also vowed to launch more long-range rockets and conduct its third nuclear test.

The nuclear threats came in defiance of a resolution issued by the UN Security Council on Tuesday that condemned Pyongyang for test-firing a missile in December and tightened existing sanctions on Kim's regime.

Pyongyang also declared that further talks on removing nuclear weapons from the Korean peninsula were now not possible, the London Telegraph reported.

Describing the UN Security Council as "a marionette of the US," North Korea's National Defense Commission said the new nuclear test would be part of its action against the "sworn enemy of the Korean people."

According to the Telegraph, North Korean state media wrote:

"The UNSC should apologize for its crime of seriously encroaching upon the independence of a sovereign state ... and repeal all the unreasonable 'resolutions' at once."

Pyongyang declared that a "nuclear test of a higher level" would be carried out.

According to a Reuters report, the commission also reaffirmed its declaration that December's rocket launch represented both a peaceful bid to send a satellite into space, and a military purpose — to build capability to strike the United States.

The National Defense Commission reportedly said:

"We are not disguising the fact that the various satellites and long-range rockets that we will fire and the high-level nuclear test we will carry out are targeted at the United States."

The hermit state was already the most heavily sanctioned country in the world before the latest UN action.

Expertd say North Korea's nuclear capabilities are still primitive and its missile technology outdated. Brian Harvey, a Dublin-based space analyst and co-author of Emerging Space Powers, said any belief Pyongyang would be able to use its satellite technology to deliver a nuclear missile is "nonsensical."

Geoffrey Cain contributed reporting from Seoul.