South Korea is set to begin production of the KF-21 fighter jet this year as planned, the state arms procurement agency said Wednesday, in what would be a major milestone in the country's pursuit of an advanced homegrown fighter.

The Defense Acquisition Program Administration seeks to sign a contract with Korea Aerospace Industries Ltd., the jet's manufacturer, within the first half of the year to pave the way for the KF-21's large-scale production, according to a DAPA official.

In 2015, South Korea launched a joint fighter jet development project with Indonesia, with the aim of deploying 120 KF-21s in the South Korean Air Force by 2032 to replace its aging fleet of F-4 and F-5 jets.

DAPA said all six KF-21 prototypes have successfully staged test flights, carrying out various performance assessments, including supersonic flights and arms separation tests.

The prototypes will continue various testing this year, DAPA said, adding that one of them will undergo extreme weather tests at the Agency for Defense Development's test center in Seosan, 98 kilometers southwest of Seoul, through February.

The joint development project worth 8.1 trillion won ($6.1 billion) through 2026 still faces uncertainties stemming from Indonesia's overdue payments, which were estimated at nearly 1 trillion won as of October last year.

Seoul has agreed to pay about 60 percent of the project's cost, with Jakarta and KAI covering around 20 percent each.

The DAPA official said talks are ongoing for Jakarta to submit an updated payment plan for the project. (Yonhap)