North Korea on Thursday said the growing US-led military buildup and expanding security cooperation between Washington, Seoul and Tokyo justify its decision to strengthen and expand its nuclear forces, with Pyongyang declaring that its status as a nuclear weapons state is irreversible.According to the Reuters, North Korea’s vice defence minister Kim Kang Il said the growing US-led military buildup and expanding security cooperation between the United States, South Korea and Japan justify Pyongyang’s efforts to strengthen and expand its nuclear forces.Speaking at the Beijing Xiangshan Forum, Kim said, “The ceaseless nuclear arms buildup of the enemy states fully justifies the building of a solid nuclear shield of the DPRK.” He added, “As the enemy states’ nuclear threat reaches the extreme level … the DPRK will firmly defend the peace and stability in the Korean Peninsula and the region by ceaselessly expanding and strengthening its self-defensive nuclear deterrent.“Kim accused the United States of pursuing what he called an “invariable” hostile policy towards North Korea and said Washington was turning its trilateral cooperation with South Korea and Japan into a “nuclear alliance.”Kim also said North Korea’s constitutional status as a nuclear weapons state was “the line of no retreat” and urged countries to abandon what he called the “daydream” of denuclearisation.The remarks came hours after Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, rejected renewed international calls for Pyongyang to denuclearise following discussions at the International Atomic Energy Agency (IAEA) General Conference.She argued that the country’s nuclear status had been permanently established both “physically and legally”, while saying the IAEA and western countries could not affect Pyongyang’s ability or determination to take measures it considers necessary to defend its interests.The latest remarks come against a backdrop of heightened military activity around the Korean Peninsula. The United States, South Korea and Japan concluded their five day Freedom Edge 26 trilateral exercise on September 11, with the drills aimed at improving coordination and readiness against North Korea’s nuclear and missile threats.Reuters reported that the exercise was followed on September 12 by North Korean launches of several short range ballistic missiles from the Wonsan area towards the sea off its east coast.North Korea later said the launches were part of a broader “joint firepower attack drill” involving five army units and multiple weapons systems, including attack drones, tactical cruise missiles, tactical ballistic missiles and large calibre multiple rocket launchers.