Ahead of planned summits with South Korean President Moon Jae-in next week and with US President Donald Trump in late May or early June, Kim told the Central Committee of the ruling Workers’ Party of Korea on Friday that he would stop nuclear tests and intercontinental ballistic rocket tests from April 21. Pyongyang would also dismantle a northern nuclear testing ground, according to a report from state-owned Korean Central News Agency.

“I solemnly declare that we have accomplished credible weaponisation of nuclear forces,” Kim was quoted as saying. 

“The northern nuclear test ground of [North Korea] will be dismantled to transparently guarantee the discontinuance of nuclear tests.” 

The Punggye-ri site, where all six of Pyongyang’s underground tests have been conducted, is North Korea’s only known nuclear test site. 

Chinese analysts had warned earlier about the risks of implosion if more tests were conducted in the area. The biggest and most recent test was in September.

While not saying what he would do with his existing arsenal of nuclear warheads, Kim pledged Pyongyang would not use the technology unless it was under serious threat.

“[North Korea] will never use nuclear weapons nor transfer nuclear weapons or nuclear technology under any circumstances unless there were nuclear threats and nuclear provocations against [North Korea],” Kim was quoted as saying.

Trump described Kim’s announcement as “good news” and later said progress was being made. 

Nevertheless, Chinese analysts were divided over whether North Korea was heading down the path to complete dismantling of its nuclear weapons.

Zhao Tong, a fellow in the nuclear policy programme at the Carnegie-Tsinghua Centre for Global Policy, said Pyongyang’s decision clearly revealed its two-step strategy: first gaining sufficient nuclear power, and then forcing the international community to accept that reality, allowing Pyongyang to press on and try to normalise ties with neighbours without giving up on its nuclear weapons.

“The main goal of the first step is to have a basic sense of security by arming itself with nuclear weapons. After that is achieved, Pyongyang’s strategic mission is to develop its economy in full force,” Zhao said.

North Korea calls for ‘total end to nukes on peninsula’ without demanding US military leaves, according to South

"Kim appears to be conceding that North Korea will not develop more powerful warheads, but I don’t think he will make any further concessions on the warheads he already has."

There is no official data on the size of Pyongyang’s arsenal but a report published by the Stockholm International Peace Research Institute in July estimated that North Korea had up to 20 warheads.

Renmin University international relations professor Cheng Xiaohe said Kim’s announcement was the first real step towards denuclearisation but the process would take years. Cheng said he was optimistic that Kim’s talks with Moon and Trump would tackle eradication of Pyongyang’s nuclear weapons.

“North Korea is ready to give up nuclear weapons on certain conditions,” Cheng said.

“Two things are at stake: whether there is a timeline for Pyongyang to denuclearise. The second is what the international community can offer Pyongyang in return.” 

Seoul said Pyongyang’s decision was “meaningful” progress and would create favourable conditions for the summits.

Japanese Prime Minister Shinzo Abe also welcomed the commitments but said they must lead to action.

“What’s important is that this leads to complete, verifiable denuclearisation,” Abe said.

Australian Foreign Minister Julie Bishop agreed, saying “verifiable steps” would be needed to ensure testing had indeed been halted.

Donald Trump: ‘good relationship formed’ when CIA chief Mike Pompeo met Kim Jong-un in secret North Korea visit

The British government said North Korea had taken a positive step that it hoped was “an effort to negotiate in good faith”.

Moon Chung-in, a special adviser on foreign affairs and national security in Seoul, said earlier this week that Kim realised he had to pay more attention to pursuing pressing economic reforms to improve the livelihood of his people.

According to Moon Chung-in, Kim has so far not demanded the withdrawal of US troops in South Korea in his recent meetings with South Korean officials, something that Pyongyang had previously insisted on as a precondition for denuclearisation.

Additional reporting by Reuters