The US Department of State has approved a possible sale to South Korea of up to 25 F-35A radar-evading fighters and related equipment to help the East Asian ally maintain a "credible" defense capability, a government agency said Wednesday.

The Defense Security Cooperation Agency under the Department of Defense made the announcement on the potential government-to-government Foreign Military Sale estimated to cost US$5.06 billion.

"The proposed sale will improve the Republic of Korea's capability to meet current and future threats by providing credible defense capability to deter aggression in the region and ensure interoperability with US forces," DSCA said in a release, referring to South Korea by its official name.

The South Korean government has requested the purchase of up to 25 F-35A fighters, along with 26 engines, electronic warfare reprogramming lab support and other pieces of related equipment, according to the release.

The DSCA delivered the required certification notifying Congress of the possible sale earlier in the day, it said, as the sale requires congressional endorsement.

In March, South Korea's Defense Project Promotion Committee approved a 3.75 trillion-won ($2.82 billion) plan to buy the F-35A aircraft through 2028. The South Korean Air Force currently maintains 40 F-35As manufactured by US defense giant Lockheed Martin.

South Korea has been pushing to bring in a new batch of F-35As to prop up the country's Kill Chain preemptive strike system, a pillar of its three-pronged deterrence program against the North's nuclear and missile threats. (Yonhap)