The sale, worth about $18 million, would provide the South Korean navy with 18 UGM-84L HARPOON Block II All-Up-Round Missiles.
Associated parts, equipment, logistical support and training would be included in the deal.
"The government of Korea is one of the major political and economic powers in East Asia and the Western Pacific and a key partner of the United States in ensuring peace and stability in that region," the agency said. "It is vital to the U.S. national interest to assist our Korean ally in developing and maintaining a strong and ready self-defense capability, which will contribute to an acceptable military balance in the area."
The agency said acquisition of the missiles, which will supplement those now in the South Korean inventory, would bring the ROK's Naval Anti-Surface Warfare performance up to existing regional baselines.