North Korean leader Kim Jong-un said he saw no reason to stick to his commitment to suspend long-range nuclear and missile tests and that soon Pyongyang will showcase a "new strategic weapon".
Washington was swift to respond, with Secretary of State Mike Pompeo urging Kim to "take a different course" and stressing that the USA wanted "peace not confrontation" with the North, while Trump played down the development.
The broadcast appeared to stand in place of Kim's usual New Year speech - normally a key moment in the North Korean political calendar.
Alongside the North Korean leader's latest sabre-rattling this week was a stunning admission: Efforts to engage the United States had failed.
Tensions between the US and North Korea have ratcheted up in recent months following the collapse of talks in February in Hanoi.
Kim "said that we will never allow the impudent U.S.to abuse the DPRK-U.S. dialogue for meeting its sordid aim but will shift to a shocking actual action to make it pay for the pains sustained by our people so far and for the development so far restrained", the KCNA report quoted him as saying, using the acronym for the North's formal name, the Democratic People's Republic of Korea.
On Tuesday, Mr. Kim addressed denuclearization saying, "If the US persists in its hostile policy toward the D.P.R.K., there will never be denuclearization on the Korean Peninsula", using the initials for the North's formal name, the Democratic People's Republic of Korea.
Unification Minister Kim Yeon-chul said in his New Year's Day address on Thursday that the two Koreas need to recover their mutual trust and create a space for inter-Korean relations.
Mr. Kim also said the world would witness a new strategic weapon "in the near future", according to the North's official Korean Central News Agency, though no details were provided. "North Korea's new "strategic weapon" might not be ready", Leif-Eric Easley, a professor at Ewha University in Seoul, said.
Negotiations between the two sides have been largely deadlocked since the breakup of their Hanoi summit in February.
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The U.S. president and top officials in his administration have said that a return to nuclear tests and launches of ICBMs capable of striking the United States would prompt a strong response by Washington - and likely signal the end of diplomacy. The administration insisted that meant Mr. Kim would give up his nuclear weapons, his stockpile of fissile material and his missiles, but the North argued that it also meant the United States would withdraw troops and offshore ships and submarines that could launch nuclear weapons.
While Trump has remained silent, United Nations (UN) secretary general Antonio Guterres says he is "deeply concerned" by Kim's statements.
"The scope and depth of bolstering our [nuclear] deterrent" will depend "on the U.S.' future attitude to the DPRK", KCNA reported, citing Kim.
In an interview, US Secretary of State Mike Pompeo said Tuesday that he hoped the North would prefer peace to war.
Kim did warn there were no longer grounds for the North to be "unilaterally bound" to its moratorium, criticizing the United States for expanding sanctions, continuing military exercises with South Korea and providing the South with advanced weaponry.
"How to respond to Kim Jong Un's threatening New Year's remarks?"
The North last lobbed intermediate-range ballistic missiles (IRBMs) over Japan on two occasions in 2017, prompting the government to send out alarms on cellphones and interrupt television programs to urge residents to take cover.
Pyongyang has claimed that it has taken substantive denuclearization steps over the past years and asked for Washington's corresponding measures, including security guarantees and lifting or easing of sanctions crippling its economy.
"We're hopeful that Chairman Kim will make the right decision, (that) he'll choose peace and prosperity over conflict and war".