The United States will “do what it can” to help resolve festering trade and political disputes between South Korea and Japan, a senior U.S. official said Wednesday after a series of meetings with Seoul officials.

David Stilwell, the top U.S. diplomat for East Asian affairs, is in South Korea for three days, as Seoul is seeking U.S. help to resolve the spat between two of America’s most important allies in the region.

After meeting with South Korean Foreign Minister Kang Kyung-wha, Stilwell told reporters that the United States places a “great priority on strengthening” its relations with South Korea and Japan.

“Fundamentally ROK and Japan must resolve the sensitive matters and we hope that the resolution happens soon,” Stilwell said, using the abbreviation for South Korea’s official name, the Republic of Korea. “United States is a close friend and ally to both. We will do what we can to support their efforts to resolve this.”

Earlier Wednesday, he met other South Korean officials including deputy national security adviser Kim Hyun-chong, who visited Washington last week for talks on the trade issue.

Kim said he explained Seoul’s position on the issue to Stilwell in details. Kim said Stilwell “sufficiently understood the seriousness of this problem.”

South Korea and Japan are closely linked economically and culturally and host a total of about 80,000 U.S. troops on their soils, the core of America’s military presence in the region. But they are often embroiled in historical and territorial disputes stemming from Japan’s 1910-45 colonial occupation of the Korean Peninsula. Such on-and-off disputes have complicated U.S. efforts to bolster trilateral cooperation to cope with North Korea’s nuclear threats and China’s growing influence.

The latest dispute flared after Japan tightened controls on high-tech exports to South Korea, potentially affecting its manufacturers and global supplies of high-tech products like smartphones and displays.

South Korean officials have warned Japan not to escalate the dispute, saying its trade restriction would also eventually damage its own economy. Last week, Kang discussed the issue with U.S. Secretary of State Mike Pompeo by phone and conveyed Seoul’s view that Japan’s “undesirable” trade curbs could disrupt global supply chains and hurt trilateral cooperation.

Seoul believes Japan was retaliating for South Korean court rulings last year that ordered Japanese companies to compensate some of their colonial-era Korean workers for forced labor.

Japan has denied that, maintaining that the sensitive materials subject to the stricter approval process can be exported only to trustworthy trading partners. Some Japanese officials including Prime Minister Shinzo Abe have suggested that critical materials with potential military applications exported to South Korea may have been eventually transferred to North Korea. Seoul denies that.

Japan maintains that all colonial-era compensation issues were settled in 1965 when the two countries signed a treaty that restored their diplomatic ties. At the time, South Korea received more than $800 million in economic aid and loans from Japan and used the money to rebuild its infrastructure and economy devastated by the 1950-53 Korean War.

When South Korea’s Supreme Court ordered two Japanese companies to compensate their former forced Korean laborers, the court said the 1965 treaty cannot prevent individuals from seeking compensation.

On Tuesday, Japanese Foreign Minister Taro Kono warned that Tokyo might take further action if South Korea pushes harder on the issues related to historical issues.

Tokyo has requested third-party arbitration of the Korean wartime labor dispute as stipulated in a 1965 treaty. The deadline for a response is Thursday, and Seoul has indicated that it will not respond.

Japanese Deputy Chief Cabinet Secretary Yasutoshi Nishimura on Wednesday urged Seoul to nullify last year’s court orders on the compensation issue and settle by arbitration. Nishimura said Japan will consider all options to protect Japanese companies.

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