Prime Minister Shinzo Abe on Thursday urged Seoul to take steps to ensure a court ruling ordering compensation for wartime forced labor does not affect Japanese businesses and indicated that Tokyo will take the case to the international stage if necessary.

“To manage difficult issues between the two countries, South Korea’s efforts are indispensable. We strongly expect the South Korean government to take positive measures against the ruling,” Abe said during a meeting of the House of Representatives Budget Committee.

South Korea’s Supreme Court on Tuesday upheld a lower court decision that ordered Nippon Steel & Sumitomo Metal Corp. to compensate four South Koreans who were victims of forced labor during Japanese colonial rule from 1910 to 1945.

Calling the ruling an “unbelievable judgment,” Abe said, “We will take resolute actions, with an eye on all possible options, including international adjudication.” He suggested Tokyo could take the case to the International Court of Justice.

The Japanese government maintains that the right to seek compensation was terminated under a pact attached to the 1965 bilateral treaty that stipulates issues relating to property and claims between the two countries and their peoples have been settled “completely and finally.”

The ruling could pour cold water on improving relations between Japan and South Korea, which need to work in tandem to deal with North Korea’s nuclear and ballistic missile programs.

Abe visited South Korea earlier this year while Moon attended a trilateral meeting that also included China in Tokyo in May.

Bilateral ties have often been rocked by issues related to territory and history, including over “comfort women,” a euphemism for those who were forced to work in Japanese wartime military brothels.

Abe expressed his “deep regret” over a series of recent events that “run counter to efforts to build forward-looking bilateral ties.”

He cited as examples a request for Maritime Self-Defense Force vessels not to fly the Rising Sun flag, used by the Imperial military in World War II, during an international naval review hosted by South Korea, and a recent visit by South Korean lawmakers to Seoul-controlled islets in the Sea of Japan that are claimed by Tokyo.

The government has started contacting Japanese companies involved in similar lawsuits in South Korea to seek understanding of its stance that they should not abide by rulings upholding South Korean individuals’ compensation claims, sources close to the matter said.

A senior Foreign Ministry official told a meeting of the ruling Liberal Democratic Party on Wednesday that, “If even one Japanese company abides by (a compensation order), it would make no sense.”

The LDP on Thursday adopted a resolution urging the government to study countermeasures, including taking the case to the ICJ.

Fourteen other similar suits have been filed against Japanese firms in South Korea, including Mitsubishi Heavy Industries Ltd., Nachi-Fujikoshi Corp. and Hitachi Zosen Corp.