A request from the Republic of Korea to the United States for upgrades to F-16 fighters has received State Department approval.

The proposed deal would be under the U.S. Foreign Military Sales program and carrier an estimated value of $2.5 billion.

U.S. Defense Security Cooperation Agency, which manages the FMS program, told Congress the sale would serve U.S. national interests.

"The ROK 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," it 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.

The proposed upgrade would be performed on 134 KF-16C/D Block 52 aircraft. It would include 150 modular mission computers, 150 active electronically scanned array radars, 150 AN/APX-125 or equivalent advanced identification-friend-or-foe Systems, 150 LN-260 embedded GPS/inertial navigation systems, and 150 upgraded radar warning receivers, as well as other systems.

A variety of bombs and missile are also covered under the deal. Among them are GBU-54 Laser Joint Direct Attack Munitions and training munitions.

"The ROK Air Force is modernizing its KF-16 fleet to better support its air defense needs," DSCA said. "This upgrade allows the ROK to protect and maintain critical airspace and provide a powerful defensive and offensive capability to preserve the security of the Korean peninsula and its vital national assets.

The principal contractors would be Lockheed Martin and Northrop Grumman.

The F-16 upgrade request is the second by South Korea. An earlier deal, involving BAE Systems, fell apart when the agreed-upon price was increased.

South Korea recently filed suit against BAE Systems and Raytheon, which was to conduct upgrades to electronic systems of the aircraft, demanding reimbursement of costs involved. BAE Systems claims the price increase was a unilateral action by the U.S. government and as such is not responsible.