SEOUL - The United States revoked the exemption of arms non-recurring costs for South Korea, raising Seoul's burden for US weapons purchases, Yonhap news agency reported Sunday, citing multiple unidentified sources familiar with the matter.

The US administration notified the South Korean government around August that it will abolish the non-recurring costs (NC) waiver granted to its key allies, including South Korea, when selling US weapons through Foreign Military Sales (FMS) program, or a government-to-government contract.

The NC refers to non-recurring costs incurred by US defense contractors when developing and producing weapons, such as development, design and testing costs.

ALSO READ: Yonhap: Trump says US reached trade deal with S. Korea

The NC exemption allowed South Korea to save about 5 percent on its US weapons purchases, but with the recent abolition, Seoul's cost burden of importing US military equipment will increase, the sources were quoted as saying.

According to the sources, a similar notification was sent to other countries, including Japan, Australia and NATO allies.

Yonhap noted that the US policy change reflected US President Donald Trump's transactional approach to alliances and his perception that allies had long enjoyed excessive surpluses in trade with the United States.

ALSO READ: South Korea cannot pay $350b to US for tariff deal as Trump suggests, top aide says

South Korean President Lee Jae-myung held a press conference in the presidential office on Friday to announce the "joint fact sheet," which finalized South Korea's tariff and security agreement with the United States.

According to the fact sheet, South Korea will spend $25 billion on US military equipment purchases by 2030.