North Korea is to abandon its moratorium on nuclear and intercontinental ballistic missile tests, Kim Jong-un has announced.
Addressing a meeting with party officials, the North Korean leader also said the country would unveil a new strategic weapon in the new future, the country's official KCNA news agency reported on Wednesday.
"There is no ground for us to get unilaterally bound to the commitment any longer," he is quoted as saying.
"The world will witness a new strategic weapon to be possessed by the DPRK in the near future."
North Korea has not tested a long-range missile or nuclear warhead since 2017 under a self-imposed moratorium.
But in recent weeks the North Koreans had been more bellicose as tensions escalated on the Korean peninsula.
Kim had signalled that Pyongyang was preparing a "gift" which would be unveiled if the US failed to make significant concessions in negotiations by the end of the year.
He paved the way for the move at a meeting of 300 top officials.
The North Koreans had been demanding the lifting of sanctions as a price for stepping up the pace of peace talks which appeared to have stalled.
His announcement will be a blow for Donald Trump who thought personal diplomacy could end decades of hostility.
A series of summits raised hopes that the US president's unconventional diplomatic approach could bear fruit.
Mr Trump, who had derided Kim as "Rocket Man", struck a different note over the summer praising the leader of the rogue regime.
The US president on Tuesday said he believed Kim would stick to his commitments on denuclearisation.
"We did sign a contract, talking about denuclearisation. That was the number one sentence, 'denuclearisation', that was done in Singapore. I think he's a man of his word," a tuxedo-wearing Mr Trump told reporters before heading into New Year festivities at his holiday retreat in Florida.
In Florida Mr Trump repeated his previous comments that he and Kim "like" each other and have a very good relationship.
"He is representing his country. We will do what we have to do," he added.
Hopes had been raised further when the two men met at the demilitarised zone (DMZ) which divides North and South Korea at the end of June.
The US president maintained that the suspension of nuclear tests was evidence that his approach had succeeded where others had failed and that Kim could be persuaded to give up his nuclear arsenal.
In Washington officials had sought to play down the threat from Pyongyang, despite the increasingly aggressive noises coming from North Korea.
But in recent months relations have worsened and the North Korean leader struck a harsh note at the meeting of the ruling Workers Party.
"The US is raising demands contrary to the fundamental interests of our state and is adopting brigandish attitude," KCNA cited him as saying.
"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".
Kim added that "if the US persists in its hostile policy toward the DPRK, there will never be the denuclearisation on the Korean Peninsula and the DPRK will steadily develop necessary and prerequisite strategic weapons for the security of the state until the U.S. rolls back its hostile policy," according to the agency.
Kim and President Donald Trump have met three times since June 2018, but negotiations have faltered since the collapse of their second summit last February in Vietnam.
The North announced in December that it performed two "crucial" tests at its long-range rocket launch site that would further strengthen its nuclear deterrent, prompting speculation that it was developing an ICBM or planning a satellite launch that would provide an opportunity to advance its missile technologies.
North Korea also last year ended a 17-month pause in ballistic activity by testing a slew of solid-fuel weapons that potentially expanded its capabilities to strike targets in South Korea and Japan, including U.S. military bases there.