"There is no ground for us to get unilaterally bound to the commitment any longer," the official KCNA news agency cited him telling top ruling party officials.

"The world will witness a new strategic weapon to be possessed by the DPRK in the near future," it cited him as saying.

Kim declared in 2018 that the North had no further need for nuclear or ICBM tests, and Wednesday's announcement threatens to upend the nuclear diplomacy of the last two years, with US President Donald Trump regularly referring to Kim's "promise" to him not to carry any out.

But nuclear negotiations between the two have been largely deadlocked since the breakup of their Hanoi summit in February, and the North set the US an end-of-year deadline for it to offer fresh concessions, or it would adopt a "new way".

Kim's statement to a full plenum of the central committee of the ruling Workers' Party made clear that the North was willing to live under international sanctions to preserve its nuclear capability.

"The US is raising demands contrary to the fundamental interests of our state and is adopting brigandish attitude," KCNA cited him as saying.

Washington had "conducted tens of big and small joint military drills which its president personally promised to stop" and sent high-tech military equipment to the South, he said, and stepped up sanctions against the North.

"We can never sell our dignity," he added, saying Pyongyang would "shift to a shocking actual action to make (the US) pay for the pains sustained by our people".