North Korea amended its constitution to bolster and expand its nuclear force, with Kim calling for more modern atomic weapons to counter the threat from the US and its allies.

North Korea has enshrined its status as a nuclear power in its constitution, with leader Kim Jong Un pointing to the growing cooperation between the United States, South Korea, and Japan as “the worst actual threat” facing the isolated nation, state media reported Thursday.

The country’s rubber stamp parliament added the law to North Korea’s constitution after meeting Tuesday and Wednesday, meaning its policy of strengthening its nuclear force is now permanent, the official Korean Central News Agency (KCNA) reported.

North Korea’s “nuclear force-building policy has been made permanent as the basic law of the state, which no one is allowed to flout,” Kim said at a meeting of the Supreme People’s Assembly, according to KCNA.

The move reinforces Pyongyang’s view that it is a forever nuclear power and that the idea of denuclearising or giving up its weapons, a key demand of the US and its Western allies, is not up for discussion.

Kim also said North Korea needed nuclear weapons to counter an existential threat from the US and its allies.

He justified Pyongyang’s accelerating weapons development programme by pointing to the trilateral military cooperation between the US, South Korea, and Japan – which he called “the worst actual threat, not threatening rhetoric or an imaginary entity,” KCNA reported.

The US has “maximised its nuclear war threats to our Republic by resuming the large-scale nuclear war joint drills with clear aggressive nature and putting the deployment of its strategic nuclear assets near the Korean peninsula permanently,” Kim said.

The North Korean leader added that the new law was “the most just and reasonable crucial step which fully meets not only the urgent requirements of the present era but also the lawfulness and the long-term requirements of building a socialist country.”

Neighbouring Japan, however, said North Korea’s atomic weapons programme was “absolutely unacceptable”.

“North Korea’s nuclear and missile development threatens the peace and security of our country and the international community,” Japan’s Chief Cabinet Secretary Hirokazu Matsuno said Thursday in response to the constitutional change.

“We will cooperate with the United States, South Korea and the rest of the international community towards the full implementation of relevant UN Security Council resolutions and the full denuclearisation of North Korea.”

Despite international sanctions over its nuclear weapons programme, North Korea has conducted a record number of missile tests this year, ignoring warnings from the US, South Korea, and their allies.

Diplomatic efforts to convince Pyongyang to give up its atomic arsenal failed, and the constitutional change came after Kim’s declaration last year that North Korea was an “irreversible” nuclear weapons state.