North Korean leader Kim Jong-un has declared that Pyongyang is abandoning its moratoriums on nuclear and intercontinental ballistic missile tests, state media reported.

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

Mr Kim declared in 2018 that the North had no further need for nuclear or ICBM tests, and this announcement threatens to upend the nuclear diplomacy of the last two years, with US President Donald Trump regularly referring to Mr 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".

Mr 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".

On Sunday, he called for "positive and offensive measures" to ensure the country's security.

US national security adviser Robert O'Brien warned Washington would be "extraordinarily disappointed" if North Korea tests a long-range or nuclear missile, while Secretary of State Mike Pompeo said he hoped it would choose peace over confrontation.

"We still maintain our view that we can find a path forward to convince the leadership in North Korea that their best course of action is to create a better opportunity for their people by getting rid of their nuclear weapons. That's our mission set," Mr Pompeo said yesterday.

The US Air Force flew an RC-135 surveillance plane over South Korea yesterday and today, according to military flight tracker Aircraft Spots.

Despite mounting speculation over a potential military provocation, any restart of an ICBM test would risk a personal relationship with Donald Trump, which Pyongyang has repeatedly touted while denouncing Mr Pompeo and other aides, analysts say.