Foreign Minister Taro Kono said Wednesday he has called on his South Korean counterpart, Kang Kyung-wha, to take “firm and resolute” action over a Supreme Court ruling ordering a Japanese steel firm to compensate four South Koreans subject to forced labor during Japan’s 1910-1945 colonial rule of the Korean Peninsula.

“As Minister Kang said, the South Korean government has started discussions as to how to address the matter. We will wait for its decision,” Kono told reporters at the Foreign Ministry following phone talks with Kang.

Kono said the government hopes Japanese nationals and companies will not be subjected to detrimental treatment as a result of the ruling, but stopped short of expanding on what kind of actions he believes should be taken.

A day earlier, Kono called the decision “very regrettable and totally unacceptable,” after the South Korean top court upheld the July 2013 ruling by the Seoul High Court that ordered Nippon Steel & Sumitomo Metal Corp. to pay 400 million won (¥39.7 million) in compensation to the workers.

The Supreme Court’s final ruling in the case is likely to have a significant impact on Japanese-South Korean ties.

Following news of the court’s decision, Kono called the South Korean Ambassador to Japan, Lee Su-hoon, to the Foreign Ministry and told him that it “fundamentally undermines the legal basis that has served as the foundation of the friendly relationship between the two countries since the normalization of bilateral relations in 1965.”

In a statement, Kono also said Japan may take the matter to the relevant international court.

Prime Minister Shinzo Abe told reporters that “the ruling this time is impossible in terms of international law,” and that “the Japanese government will react in a resolute manner.”

The four claimants in the case, only one of whom remains alive today, had said they were deprived of their human rights when they were forced to work at a steel mill belonging to Japan Iron & Steel Co. The firm was later known as Nippon Steel Corp., until it merged with another steel-maker in 2012 to form Nippon Steel & Sumitomo Metal.

Japan’s government has taken the position that the issue of compensation is “completely and finally” resolved, as declared by a 1965 pact attached to the Japan-South Korean treaty that normalized their post-colonial relationship.

But Tuesday’s decision by South Korea’s top court found that the right of the plaintiffs to file claims as individuals had not expired, despite the accord with Japan.

Nippon Steel lodged an appeal in August 2013 against the earlier Seoul High Court ruling, contending that the issue of compensation had already been settled under the 1965 pact. The company issued a statement Tuesday saying the ruling was “extremely regrettable,” adding that it will respond “properly” after examining the contents of the ruling and taking into account the Japanese government’s response.

The top court’s decision represents the first final ruling in South Korea concerning a compensation order against a Japanese company following a post-World War II compensation lawsuit.

The decision suggests firms involved in similar lawsuits could face similar outcomes. Among the other Japanese firms that have lost cases in lower courts in South Korea are Mitsubishi Heavy Industries Ltd. and Hitachi Zosen Corp.

Tuesday’s ruling “not only clearly violates the Japan-South Korea pact on rights to claim, but also inflicts unfair damage on a Japanese company,” Kono told the South Korean ambassador in Tokyo. The initial part of the meeting was open to media.

“What is happening right now is unthinkable in terms of international common sense and in a country that upholds the rule of law,” Kono said.

Kono also urged Seoul to “immediately take necessary measures” to prevent any further detrimental impact on Japanese people or businesses.

Despite Tokyo’s efforts to foster bilateral relations with Seoul in a forward-looking manner, wartime history continues to cast a pall over ties. Contentious issues include not only South Koreans who were subject to forced labor, but also the issue of “comfort women” — a euphemism that refers to women and girls forced to provide sex for Japanese troops before and during World War II.