SEOUL - The upgraded missiles will provide South Korea with an enhanced capability to defend against ballistic missile, aircraft threats from North Korea.
South Korea seeks to procure 121 units of advanced US patriot missiles worth US$404 million (S$500 million) as part of efforts to establish its own air defence system to deter North Korea's increasing missile threats.
To be launched in the early 2020s, the Korea Air and Missile Defence programme is a low-tier, multiple-interception shield designed to strike incoming missiles at an altitude of 40-50 kilometres.
The US Defence Security Cooperation Agency said it notified Congress on Friday that Seoul sounded out the agency about a possible sale of Patriot Anti-Tactical Missiles and related equipment, parts, training, data and logistical support.
The Washington-based DSCA is an affiliate of the US Defence Department and handles government-to-government "foreign military sales."
If the deal is approved, the US administration mediates between Seoul and Massachusetts-based Raytheon Company, the principal contractor, under the FMS scheme.
Korea wants to upgrade the current patriot missiles with the Guided Enhanced Missile-Tactical configuration, an improved version of the Patriot Advanced Configuration-2 missile, a key component of the KAMD.
"These upgraded missiles will provide the ROK (South Korea) with an enhanced capability to defend against ballistic missile, aircraft and cruise missile threats," the DSCA said on its website.
"The proposed sale of ATMs (and subsequent upgrade to GEM-T) contributes to the ROK's goal to develop a more capable defence force and enhance interoperability with US forces."
The envisioned deal reflects Seoul's efforts to build an independent missile shield though the system would be interoperable with the Washington-led multinational missile defence scheme.
Defence Minister Kim Kwan-jin reaffirmed earlier this month that South Korea would not join the US programme and was not mulling the purchase of its core assets such as the Terminal High-Altitude Area Defence system and ship-based Standard Missile-3.
The issue was expected to be discussed in Washington last Thursday between Kim Jang-soo, chief of Cheong WaDae's national security office, and Susan Rice, national security advisor at the White House.
During his four-day trip through Saturday, Rice and he agreed to create a hotline to ramp up cooperation between the two countries' top security offices and discussed other bilateral and regional issues including North Korea's nuclear programme and Seoul's recent request for a delay of the transfer of wartime operational control scheduled for end-2015.
"There is a difference between the KAMD and the US MD scheme. We will strive to boost synergy by sharing what needs to be shared and interlocking what needs to be interlocked," a senior Seoul official told reporters in Washington last week on condition of anonymity due to the sensitivity of the matter.
"It is natural to exchange intelligence each other or link early warning and command systems. But it would be wrong to overinterpret that as taking part in the US MD programme."