South Korea on Monday ruled out any future negotiation over who should pay for a US advanced missile defense system to be deployed here, but left open the possibility that the Trump administration might use the issue as leverage against Seoul during the allies’ defense-sharing negotiations scheduled to take place next year.

Citing the Status of Forces Agreement and a classified separate agreement with US Forces in Korea, the Defense Ministry stressed that the allies had agreed that the US would pay for the deployment and operation of the Terminal High Altitude Area Missile Defense system, with Seoul providing land and supporting infrastructure.

“The cost sharing over THAAD was already agreed between South Korea and the US. It is also stipulated in the SOFA. I don’t think it is a matter for renegotiation,” ministry spokesperson Moon Sang-kyun said at a regular press briefing.

The spokesperson, however, refused to comment on the possibility that the US may demand a spike in South Korea’s share of the cost of stationing US Forces in Korea for the THAAD-related expenses.

The comments came after the US’ national security adviser Gen. H.R. McMaster said in an interview with Fox News on Sunday that the US would adhere to the initial agreement with South Korea until “any renegotiation.” He also said he would “never contradict“ his president, who on Friday said that he wanted South Korea to foot the bill for the $1 billion won defense system.

In interviews with Reuters and Washington Times, Trump said “it is appropriate” for South Korea to pay for THAAD. The South Korean government refuted the suggestion, saying it had not been informed about such a request from Washington.

“The question of what is the relationship on THAAD, on our defense relationship going forward, will be renegotiated as it’s going to be with all of our allies, because what the president has said is he will prioritize American citizens’ security and interests,” McMaster said.

His remark appeared to strike a different tone from Cheong Wa Dae, which claimed a day earlier that McMaster and his counterpart Kim Kwan-jin “reaffirmed” the previous agreement that the US would finance deployment, operation and maintenance of a battery for the THAAD system.

Alarmed by growing controversy over what appeared to be contradicting views between the allies’ top security advisers, Cheong Wa Dae issued a statement, saying they view McMaster’s remark as a sign of “reaffirmation.”

In a meeting with local reporters, Foreign Minister Yoon Byung-se echoed the view, saying that the main focus of McMaster’s remark was his pledge to “honor the agreement between the allies” and that it was not a comment on renegotiation.

Although the Trump administration is unlikely to seek a change to the THAAD agreement independently, Washington could link the issue to defense cost-sharing negotiation and seek a better deal when they discuss how to share the burden for hosting US troops next year, analysts said.

Since 1991, the US and South Korea have negotiated a Special Measures Agreement, which determines Seoul’s contribution to the costs of stationing USFK, such as those related to South Korean labor, utilities, rent, and construction. Under the terms of the current ninth SMA, Seoul pays roughly $828 million.

“I don’t think McMaster is in a position to refute what Trump said. We are going to negotiate the burden-sharing deal next year, I believe they will try to incorporate their demand into the negotiation process,” said Shin Bum-cheol, a professor at Korea National Diplomatic Academy.

By Yeo Jun-suk (jasonyeo@heraldcorp.com)