North Korean leader Kim Jong Un has said unification with the South is no longer possible, and that the constitution should be changed to designate it the “principal enemy”.
Mr Kim also said three organisations dealing with reunification would be dismantled.
South Korea’s president Yoon Suk Yeol, said it would respond “multiple times stronger” to any provocation from the North.
The two Koreas have been divided since the Korean War ended in 1953. They did not sign a peace treaty and therefore have remained technically still at war ever since.