South Korea plans to sign a government-to-government deal to buy 40 F-35 jets from U.S. aerospace giant Lockheed Martin during the third quarter of this year, the Defense Acquisition Program Administration (DAPA) said Monday.The state-run arms procurement agency approved the plan to buy 40 F-35 fighters starting from 2018, with an option to buy 20 more later depending on the security situation and budget, reported the S.Korean Yonhap news agency today.Seoul confirmed the decision two months after it voted down Boeing’s F-15 Silent Eagle, the only aircraft that met the previous competition’s budget of 8.3 trillion won (US$7.2 billion) for 60 jets. “Once DAPA approves the revised purchase plan between February and March, we will push to sign a deal in the third quarter after conducting flight testing and negotiations,” Air Force Brig. Gen. Jung Kwang-sun, DAPA’s aircraft department director, said in a briefing, relayed by Yonhap.According to officials, DAPA earlier estimated 7.4 trillion won for 40 F-35, which includes infrastructure and armament, while the state-run Korea Institute for Defense Analyses is set to conduct another analysis to confirm the program budget.The total budget will be confirmed after consultations with the finance ministry, which handles budget allocation, they noted. As the F-35 is sold only through the U.S. foreign military sales (FMS) program, DAPA is expected to purchase the aircraft through a government-to-government deal and without an open bid. The FMS condition requires a foreign government to pay the amount specified by the U.S. government for the F-35s at the time of payment.In response to rising concern, Lockheed Martin last month said it would offer comprehensive support for South Korea’s indigenous fighter jet projet and launch of a military communications satellite despite the reduced order quantity from 60 to 40.Seoul’s decision to buy the F-35 stealth jet comes amid calls for a fifth-generation fighter as neighboring China and Japan navigate territorial disputes and seek to expand their military power. Russia is also preparing to equip its Air Force with stealth jets to counter the U.S.’ F-35s and F-22s.