The powerful sister of North Korean leader Kim Jong Un has mocked Washington and its Asian allies for what she called their "daydream" of denuclearising the North.
She insisted the country will never give up its nuclear weapons programme.
The statement by Kim Yo Jong, one of the country's top foreign policy officials, was in response to a meeting last week between the top diplomats of the United States, South Korea and Japan where they reaffirmed their commitment to push for the North's denuclearisation.
Noting North Korea's goals for nuclear weapons expansion are enshrined in its constitution, she insisted any external discussions of denuclearisation constitute "the most hostile act" and amount to a denial of her country's sovereignty.
"If the US and its vassal forces continue to insist on anachronistic 'denuclearization' ... it will only give unlimited justness and justification to the advance of the DPRK (North Korea) aspiring after the building of the strongest nuclear force for self-defence," she said in comments released by state media.
She said North Korea's nuclear weapons status can "never be reversed by any physical strength or sly artifice".
Tensions in the regions have increased as Kim continues to flaunt his military nuclear capabilities and align with Russia over president Vladimir Putin's war on Ukraine. He is ignoring calls by Seoul and Washington to resume denuclearisation talks.
US President Donald Trump has said he would reach out to Kim again to revive diplomacy, but the North has not responded to that offer. The two men met three times during Trump's first term, but their diplomacy quickly collapsed over disagreements about ending US-led sanctions in return for North Korea taking steps to wind down its nuclear and missile programmes.
Kim's foreign policy priority is now Russia, which he has supplied with weapons and troops to help prolong its war-fighting in Ukraine.
Seoul fears Kim may receive economic assistance and advanced technology to develop his arsenal in exchange for its military supporting Russia.
Kim Yo Jong's statement came a day after South Korea fired warning shots to repel a group of North Korean soldiers who had crossed the border.
South Korea's Joint Chiefs of Staff said about 10 North Korean soldiers, some carrying weapons, violated the military demarcation line in the eastern section of the border. When South Korea issued warnings and fired warning shots, they did not return fire and returned to North Korea.
It was not immediately clear whether acting president Han Duck-soo discussed the North Korean nuclear threat with Trump during a telephone conversation on Tuesday.
Trump said in a social media post that the two leaders discussed tariffs, trade and Seoul's payment for what he called the "big time" military protection the United States provides to South Korea. There are concerns in Seoul he might push South Korea to pay significantly more of the costs for the some 28,000 US troops stationed in the country.
