"Seoul will never allow a nuclear-armed North Korea, and every effort will be made to get the country to give up its weapons of mass destruction program," a ministry official, who spoke anonymously, said.
The statements were made as the unification ministry unveiled its five-year policy plan.
Officials also said that they will work to promote cooperation between the two countries if progress is made on the nuclear issue, the Yonhap News Agency reported.
"If conditions become favorable, Seoul can allow the resumption of economic cooperation and fresh investments to the North, though no immediate steps are being taken to lift the ban," the official said.
South Korea broke all cooperative ties, except for those at the Kaesong Industrial Complex, after North Korea sunk one of its warships in 2010 and killed 46 sailors.