North Korea threatens nuclear build-up after US, South deal

North Korea's Kim Yo Jong, the powerful sister of leader Kim Jong Un, said a US, South Korea agreement this week about the need to shore up South Korean security will worsen the situation, according to state media KCNA on Saturday.

North Korea is convinced it must further perfect a "nuclear war deterrent" as a result, Kim said. The statement did not elaborate.

Kim's statement is North Korea's first comment on the meeting, and suggests its cycle of military shows of force and weapons development will continue.

US President Joe Biden and South Korean President Yoon Suk Yeol met this week, with the United States pledging to give South Korea more insight into its nuclear planning over any conflict with North Korea amid anxiety over Pyongyang's growing arsenal of missiles and bombs.

A US Navy nuclear-armed ballistic missile submarine (SSBN) will also visit South Korea for the first time since the 1980s, to help demonstrate Washington's resolve to protect the country from a North Korean attack.