North Korean leader Kim Jong Un, expressing deep frustration over stalled nuclear talks, warned of unspecified “shocking” action and said his country will soon reveal a new “strategic weapon” to the world as its bolsters its nuclear deterrent in face of “gangster-like” US pressure.

He also said North Korea is no longer obliged to maintain a self-imposed suspension on the testing of nuclear weapons and intercontinental ballistic missiles, which president Donald Trump has touted as a major diplomatic accomplishment.

However, Kim gave no clear indication that a resumption of such tests was imminent and appeared to leave the door open for eventual negotiations.

He has used the diplomatic stalemate to expand his military capabilities by intensifying tests of shorter-range weapons.

His arsenal is now estimated to include 40-50 nuclear bombs and various delivery systems, including solid-fuel missiles designed to beat missile-defence systems and developmental ICBMs potentially capable of reaching the US mainland.

Kim has also strengthened his negotiating position, moving the diplomacy closer to an arms reduction negotiation between nuclear states rather than talks that would culminate in a unilateral surrender of the weapons he sees as his strongest guarantee of survival.

Lee Sang-min, spokesman for South Korea’s Unification Ministry, said North Korea carrying out its threat to showcase a new strategic weapon would be unhelpful for diplomacy.

Strategic weapons usually refer to nuclear-capable delivery systems such as ICBMs, but North Korea has otherwise has been vague about what new arms it would display. It announced in December that it had performed two “crucial” tests at its long-range rocket launch site which would further strengthen its nuclear deterrent.

Kim’s comments, published in state media on Wednesday, were made at a key, four-day meeting of the ruling Workers’ Party’s Central Committee as talks between Washington and Pyongyang have faltered over disagreements on disarmament steps and the removal of sanctions.

Some experts say North Korea, which has always been sensitive about electoral changes in US government, will avoid serious negotiations in the coming months as it watches how Trump’s impending impeachment trial over his dealings with Ukraine affects US presidential elections in November.

Kim may instead seek to strengthen his leverage by promoting a united front with Beijing and Moscow, Pyongyang’s traditional supporters, which seek to establish themselves as major stakeholders in North Korean diplomacy. Both have called for the UN Security Council to consider easing sanctions on the North to spur progress in nuclear negotiations.

Last year Kim had said the North would pursue a “new way” if the Trump administration did not make concessions to salvage the negotiations by the end of December.

His defiant words entering 2020 indicate that his “new way” could be a patient determination to wait out sanctions and pressure, which will possibly weaken over time, while cementing the country’s status as a nuclear state.

At the party meeting Kim declared that the North will never give up its security for economic benefits in the face of what he described as increasing US hostility and nuclear threats, the Korean Central News Agency said.

“(Kim) said that we will never allow the impudent US to abuse the DPRK-US 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 agency said, referring to the North by its formal name, the Democratic People’s Republic of Korea.

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 US rolls back its hostile policy”, KCNA said.

“(Kim) confirmed that the world will witness a new strategic weapon to be possessed by the DPRK in the near future, declaring that we cannot give up the security of our future just for the visible economic results … now that hostile acts and nuclear threat against us are increasing,” it added.

On Tuesday, Trump urged Kim to stick to his alleged commitment to denuclearise.

After their first summit in Singapore in June 2018, the two leaders issued a vague statement on a nuclear-free Korean Peninsula without when and how it would occur.

“Look, he likes me, I like him, we get along,” Trump said as he walked into a New Year’s Eve party at Mar-a-Lago. “But he did sign a contract, he did sign an agreement talking about denuclearisation … I think he’s a man of his word so we’re going to find out, but I think he’s a man of his word.”