The U.S. Defense Security Cooperation Agency, in its notification to Congress, said the package would be for 112 Patriot missiles in the enhanced missile-tactical configuration.
The upgrade would be performed under a direct commercial sale arrangement rather than through the deal.
"The ROK [Republic of Korea] continues to be an important force for peace, political stability, and economic progress in North East Asia," the agency said. "These upgraded missiles will provide the ROK with an enhanced capability to defend against ballistic missile, aircraft and cruise missile threats.
The proposed sale ... contributes to the ROK's goal to develop a more capable defense force and enhance interoperability with U.S. forces."
The main contract would be Raytheon. U.S. government or contractor representatives would be required to travel to South Korea on a temporary basis for logistics support, the agency said.