SEOUL — South Korea and the United States have agreed to conduct discussions in a "reasonable and fair" way on how to share the cost for the upkeep of American troops here, a foreign ministry official here said on Tuesday.

The two sides talked about the upcoming negotiations over Seoul's share of the cost for the stationing of the 28,500-strong US Forces Korea (USFK) for next year, when US National Security Adviser John Bolton visited Korea last week, the official said.

The local daily Joong Ang Ilbo reported that Washington has tentatively decided to request that Seoul pay US$5 billion under a renewed bilateral cost-sharing arrangement for next year, more than a fivefold increase from the previous year.

"When US National Security Adviser John Bolton was visiting Korea on July 23 and 24, South Korea and the US agreed to have consultations over the sharing of the defense cost in a reasonable and fair direction," the official said on condition of anonymity.

"We believe that the specific size of the defense cost sharing is a matter that should be discussed in the 11th SMA negotiations," he added.

The official was referring to the Special Measures Agreement (SMA), a bilateral cost-sharing deal. The allies are expected to launch new SMA negotiations in the coming months, as the current one-year deal is set to expire on December 31.

During a parliamentary session, Foreign Minister Kang Kyung-wha said that Seoul and Washington share the understanding that the two sides should lead their consultations "toward the fair, reasonable defense cost sharing."

"When John Bolton was visiting Korea last week, there was an exchange of views (on the issue) in principle, but there were no consultations on the specific amount (of the cost)," Kang said.

"The South Korea-US alliance is key to peace and stability not only on the Korean Peninsula but also in Northeast Asia. As there is also a contribution that we are to make to the alliance, we will try to make an agreement as we conduct the negotiations," she added.

Under the 10th SMA, which was struck in February following months of grueling negotiations, Seoul agreed to pay 1.04 trillion won (US$879 million), an increase of 8.2 per cent from 960 billion won the previous year.

Seoul has been bracing for the new round of negotiations, with expectations that Washington will demand a hefty rise in its share of the defense cost, given that US President Donald Trump has pressured American allies to jack up their defense costs.

Another Seoul official said that both Seoul and Washington recognise the need to promptly launch the SMA negotiations.

"As the current deal will remain effective until the end of this year, the US sufficiently understands the need for the SMA consultations to start promptly," the official told Yonhap News Agency on condition of anonymity.

Since 1991, Seoul has shouldered partial costs under the SMA for Korean civilians hired by the USFK, the construction of military facilities to maintain the allies' readiness and other forms of support. — YONHAP