SEOUL, Dec. 27 (Yonhap) - South Korea's arms procurement agency said Wednesday it signed a contract with the U.S. government earlier this month to buy 20 additional F-35A stealth fighter jets amid efforts to bolster response capabilities against North Korean military threats.

The Defense Acquisition Program Administration (DAPA) signed the letter of acceptance for the purchase of the fighter jets built by U.S. aerospace company Lockheed Martin on Dec. 8, following Washington's approval of the sale in September.

Currently, the South Korean Air Force has 39 F-35A fighters after purchasing 40 F-35As from 2019 to 2022. The Air Force decided to retire an F-35A stealth jet earlier this month as it was seriously damaged by a bird strike last year.

The 20 F-35A stealth fighter jets, to be delivered to South Korea starting in 2027, will have enhanced arms operational capabilities and security features compared with the existing F-35As, according to DAPA.

The F-35A is a key asset for the South Korean military due to its high-performance radar and stealth capabilities, enabling it to carry out long-range strategic strikes without being noticed by the enemy.

DAPA said it expects the latest purchase to enhance the military's "three-axis" defense system, which consists of the Korea Massive Punishment and Retaliation, an operational plan to incapacitate the North Korean leadership in a major conflict; the Kill Chain pre-emptive strike platform; and the Korea Air and Missile Defense system.

South Korea currently operates some 410 fighter jets, including F-35As, KF-16s and F-15Ks, while North Korea has around 810 fighters, according to the 2022 Defense White Paper released earlier this year.

"Although North Korea has more fighter jets, their operation rate is known to be extremely low due to poor maintenance from a lack of parts," Shin Jong-woo, a senior analyst at the Korea Defense & Security Forum, said, citing U.N sanctions imposed due to Pyongyang's nuclear and missile programs.

Shin said the F-35A is incomparable to the North's aging fleet of fighter jets in terms of capabilities, noting that North Korea's most advanced aircraft is an early version of Russia's MiG-29, developed in the 1970s.

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