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 shut down, state media KCNA reported.
South Korea’s president 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.
In a speech delivered at the Supreme People’s Assembly – North Korea’s rubber-stamp parliament – Mr Kim said that the constitution should be amended to educate North Koreans that South Korea is a “primary foe and invariable principal enemy”.
He also said that if a war breaks out on the Korean peninsula, the country’s constitution should reflect the issue of “occupying”, “recapturing” and “incorporating” the South into its territory.
Mr Kim – who replaced his father, Kim Jong-il, as North Korean leader in 2011 – said the North “did not want war, but we also have no intention of avoiding it”
He said he was taking a “new stand” on north-south relations, which included dismantling all organisations tasked with reunification.
Speaking to his cabinet on Tuesday, South Korean President Yoon Suk Yeol said that if the North carried out a provocation, the South “will retaliate multiple times stronger”, pointing to the South Korean military’s “overwhelming response capabilities”.