U.S. Secretary of State Mike Pompeo recently expressed his support for Japan’s stance that the issue of compensation for wartime forced labor was settled by a 1965 agreement between Tokyo and Seoul, Japanese government sources said Wednesday.

The compensation issue is at the heart of a bitter diplomatic feud between Japan and South Korea that has escalated into a tit-for-tat tightening of export controls.

Pompeo’s backing was conveyed to Foreign Minister Taro Kono during a meeting earlier this month in Bangkok, where they attended a series of gatherings involving the Association of Southeast Asian Nations.

Pompeo voiced concern over the growing enmity between the two U.S. allies, according to the sources.

Kono responded that the compensation issue for wartime forced laborers during Japan’s 1910-1945 colonial rule of the Korean Peninsula has already been resolved by the 1965 agreement to settle property claims after the war, under which Tokyo provided Seoul with financial aid.

Overturning agreements stemming from the 1951 Treaty of San Francisco, which marked Japan’s re-establishment of diplomatic ties with the Allied Powers, would fundamentally undermine the international order established after the end of World War II, a source quoted Kono as saying.

While supporting Kono’s statement, Pompeo also called on Japan and South Korea to hold talks to find a forward-looking way to resolve their differences, the sources said.

With Pompeo’s backing, senior Japanese officials are expected to urge their South Korean counterparts to follow through on the 1965 accord when they meet in Guam later this week to discuss ways to de-escalate the heightened bilateral tensions.

The talks, expected to take place Friday and Saturday, are being arranged in an “unofficial” capacity without a formal announcement. The neutral setting was chosen to avoid drawing a heated public response from either side, according to diplomatic sources.

Vice Foreign Minister Takeo Akiba will represent Japan, while South Korea’s delegation will be led by First Vice Foreign Minister Cho Sei-young.

Tokyo is expected to repeat calls that Seoul should prevent Japanese companies from incurring losses following South Korean court decisions ordering compensation for people who claimed they were victims of forced labor.

Lawyers for the plaintiffs have seized assets of the companies, including Nippon Steel Corp. and Mitsubishi Heavy Industries Ltd., and are trying to liquidate them, a process that is expected to take several months.

According to the sources, Tokyo grew concerned in February that the South Korean plaintiffs would also attempt to seize Japanese companies’ assets in the United States and had been lobbying Washington to reject any such claims.

While Japan is eager to seek a solution, it rejected an offer South Korea made in June to establish a fund to compensate the plaintiffs with contributions from both Japanese and South Korean companies.

During the Guam meeting, the senior officials may also discuss tighter export controls that the countries have recently imposed on each other, as well as a bilateral military intelligence-sharing pact that may be at risk because of the worsening ties.

A decision on whether to extend the General Security of Military Information Agreement is due on Aug. 24. South Korea has recently suggested it may pull out of the pact, which enables the countries to share information about North Korean missile threats.