Chief Cabinet Secretary Yoshihide Suga’s recent comment that ties with South Korea are in a “severe state” signals that simmering tensions between the neighbors and U.S. security allies could worsen.

Tokyo and Seoul have sparred over rulings by South Korea’s top court that two of Japan’s largest companies must pay compensation to Koreans forced into labor during Japan’s 1910-1945 colonial rule.

On Tuesday, a South Korean district court said it had approved a request to seize South Korean assets of Japanese steel-making giant Nippon Steel & Sumitomo Metal Corp. in a wartime forced labor case.

Lawyers representing South Korean plaintiffs had requested in late December that the Daegu District Court in the country’s southeast seize Nippon Steel’s shares in a joint venture with South Korean steel-maker Posco. The move follows a ruling by South Korea’s Supreme Court in October ordering the company to pay 400 million won (about $350,000) to four South Koreans for their forced labor during the era of Japanese colonial rule.

On Sunday, Prime Minister Shinzo Abe said he would consider countermeasures to protect Nippon Steel assets from seizure by South Korean courts. “Relations between Japan and South Korea are in a severe state,” Suga, Japan’s top government spokesman, told a regular news conference in Tokyo on Monday, calling recent moves by Seoul “regrettable.”

Mistrust between the two neighbors has also grown as both sides trade accusations about who was in the wrong over a December incident in which Japan claims a South Korean naval vessel locked its fire-control radar onto a Japanese patrol aircraft. Seoul has argued that the plane was flying in a “provocative” manner, and is calling on Tokyo to apologize.

On Monday, Liberal Democratic Party lawmakers at a joint meeting of the LDP Policy Research Council’s National Defense Division and the Research Commission on National Security called for U.N. Security Council discussions on the incident. Several participants called for tough action against South Korea, and one requested that the talks between the two countries’ defense authorities be halted in order to take the issue to the U.N. Security Council.

Also on Monday, South Korea added six languages to its video of the incident, apparently to convey its position to the international community. In addition to Korean and English versions that had already been released, the Ministry of National Defense released the video in Chinese, Russian, French, Spanish, Arabic and Japanese.

The two countries have long wrangled over whether Japan has properly atoned for its occupation of the Korean Peninsula, which ended with Japan’s defeat in World War II. The disputes have flared anew since the 2017 election of South Korean President Moon Jae-in, whose administration has moved to disband a fund set up to compensate wartime “comfort women” — a euphemism used to refer to women who provided sex, including those who did so against their will, for Japanese troops before and during World War II — and has backed Koreans’ efforts to pursue claims of forced labor.

Abe said on NHK’s “Sunday Debate” program that he has “requested relevant departments to study specific measures based on international law” to prevent South Korea from seizing company assets. He called a bid by plaintiffs to get the court to confiscate company property “very regrettable.”

The prime minister said a 1965 treaty that normalized relations between the countries resolved all matters regarding compensation claims.

Before Suga spoke, South Korea’s Foreign Ministry said they expected a sincere response from Japan and declined to directly address Abe’s comment. The foreign ministers from the two countries talked last week by telephone, South Korea said. Last month, officials from both countries said they were speaking with each other on ways to address the court’s decisions.

In the rulings, Mitsubishi Heavy Industries Ltd. was ordered to pay as much as $134,000 to each of the 10 people subject to forced labor while Nippon Steel was ordered to pay $88,000 each to four plaintiffs. There are more than a dozen such cases pending in South Korea involving about 70 companies, according to the Ministry of Foreign Affairs, which refers to the claimants as “former civilian workers from the Korean Peninsula.”

Japan and South Korea were each other’s third-largest trading partners in 2017, with more than $82 billion in total trade between the two sides. Although simmering tension between Japan and South Korea has led to protests on Seoul’s streets and calls to boycott Japanese products, the previous disputes have never escalated to the point where they caused serious economic damage. Still, the political situation in both countries provides little incentive to reach a speedy resolution this time around.

A Dec. 14-16 poll by the Yomiuri Shimbun found 86 percent of respondents agreed that all forced labor claims were settled under the 1965 treaty. Public opinion will become increasingly important for the conservative Abe in the run-up to the Upper House election in July. Moon, a progressive, saw his disapproval rate exceed his approval rating for the first time since taking office in May 2017, with many respondents saying the president lacked the ability to solve South Korea’s economic issues.