South Korea's top security aide said that Seoul plans to build a nuclear-powered submarine on its own soil.

Speaking during a parliamentary audit of the presidential office on Thursday, National Security Adviser Wi Sung-lac said the government is not considering building the submarine in the United States, emphasizing that it intends to develop a vessel tailored to South Korea's needs.

Wi noted that the 78-hundred-ton Virginia-class submarine, which costs over five trillion won, or roughly three-point-four billion U.S. dollars, is unnecessary for South Korea’s purposes, stressing that the nation will pursue a realistic, cost-effective vessel.

He also dismissed the possibility of investing in facilities in Philadelphia or asking the U.S. manufacturer General Dynamics to build South Korea’s submarines, calling both options “unrealistic.”

Wi said that no uranium enrichment level has been selected yet, but that possibilities include fuel with less than 20 percent enrichment.