SEOUL, South Korea (AP) — South Korea’s government said Saturday it will not attend a memorial service near Japan’s Sado Island Gold Mines due to disagreements with Tokyo over the event, which stirred longstanding tensions over the abuse of Korean forced laborers at the site before the end of World War II.

The decision marked a rare display of friction between the countries since the 2022 inauguration of South Korean President Yoon Suk Yeol. Yoon has prioritized improving relations with Japan following years of disputes over their bitter history and solidifying three-way security cooperation with Washington to counter North Korean nuclear threats, but has faced accusations at home that he was neglecting the suffering of Korean survivors.

South Korea’s Foreign Ministry said in a statement it was impossible to settle the disagreements between both governments before the planned event near the mines on Sunday.

Masashi Mizobuchi, assistant press secretary at Japan’s Foreign Ministry, called the South Korean decision “disappointing." He said Japan has thoroughly communicated with the South Korean side, but declined to comment on details of the diplomatic exchanges.

Some South Koreans had criticized Yoon’s government for throwing its support behind an event without securing a clear Japanese commitment to highlight the plight of Korean laborers.

South Korean sentiment over the event worsened after the Japanese government said this week it would send Akiko Ikuina, a parliamentary vice minister, to the event. Ikuina had reportedly visited Tokyo’s controversial Yasukuni Shrine following her election as a lawmaker in 2022. The shrine honors the country’s 2.5 million war dead, including convicted war criminals. Japan’s neighbors view the shrine as a symbol of the country’s past militarism.

In an interview with MBN television, South Korean Foreign Minister Cho Tae-yul acknowledged that Ikuina’s Yasukuni visit was an issue of contention between the countries’ diplomats.

“That issue and various other disagreements between diplomatic officials remain unresolved, and with only a few hours remaining until the event, we concluded that there wasn’t sufficient time to resolve these differences,” Cho said. “We notified them of our decision in the afternoon.”

There were also complaints over South Korea agreeing to pay for the travel expenses of Korean victims’ family members who were invited to attend the ceremony.

Ties between Seoul and Tokyo have long been complicated by grievances related to Japan’s brutal rule of the Korean Peninsula from 1910 to 1945, when hundreds of thousands of Koreans were mobilized as forced laborers for Japanese companies, or sex slaves at Tokyo’s military-run brothels during World War II. Many forced laborers are already dead and survivors are in their 90s.

Historians say hundreds of Koreans were forced to labor at the Sado mines under abusive and brutal conditions during World War II. Japan’s government has said Sunday’s ceremony will pay tribute to “all workers” who died at the mines, without specifying who they are. Critics saw this as part of a persistent policy of whitewashing Japan’s history of sexual and labor exploitation before and during the war.

The 16th-century mines on the island of Sado, off the western coast of Niigata prefecture, operated for nearly 400 years before closing in 1989 and were once the world’s largest gold producer. The mines were designated as a UNESCO World Heritage site earlier this year after Tokyo and Seoul settled a yearslong dispute. South Korea withdrew its opposition to the listing after Japan agreed to acknowledge Korean suffering more clearly in the site’s exhibition and to include Koreans in a memorial ceremony.

Mizobuchi said Tokyo expects that the event will be held by the local representatives as planned, in line with a Japanese government statement released during the July meeting of the UNESCO World Heritage committee, where it was decided to register the mines as a cultural heritage site.

In 2023, Yoon took a major step toward improving ties with Japan that had deteriorated for years over historical grievances and trade disputes, by announcing a plan to compensate Korean forced laborers from the colonial period without requiring contributions from Japanese companies.

Yoon’s plan, which relies on money raised in South Korea, drew an immediate backlash at home from former forced laborers and their supporters, who had demanded direct compensation from the Japanese companies and a fresh apology from the Japanese government.

__ AP writer Mari Yamaguchi in Tokyo contributed.