If the court upholds the order that the company pays compensation, the former labourers could request a seizure of Nippon Steel's property in South Korea, which could lead to an global arbitration, said Jin Chang-soo, president of the Sejong Institute think-tank.
The ruling is expected to drive another wedge between the Asian neighbors while opening the door for other Korean victims to ask for unpaid wages more than 70 years after their conscription.
Japan's Foreign Minister Taro Kono says Tuesday's ruling by South Korea's Supreme Court on wartime labor is totally unacceptable, and that his country will respond resolutely. Kono said Tokyo will weigh "every option", including taking the matter to an global court unless appropriate action is taken by Korea immediately.
"Above all, the decision completely overthrows the legal foundation of the friendly and cooperative relationship that Japan and the Republic of Korea have developed since the normalization of diplomatic relations in 1965", he said.
If Nippon Steel refuses to compensate, the plaintiffs could request a seizure of the company's property in South Korea, which may result in an exit of some Japanese businesses, a cut in investment and a flare-up in anti-Japanese sentiment.
Nippon Steel said it would carefully review the court decision, taking into account the Japanese government's response.
Lee said he felt "sorry for the pain victims of forced labor had to go through" and said local authorities would try to "heal their wounds".
"The government hopes to improve South Korea-Japan bilateral relations in a future-oriented manner", it added.
Choi told the press ahead of this year's Ari Cup that the aim of such events was to leave politics behind so they can continue independently if ties deteriorate.
Biegun's failure to hold direct talks with Choe is the latest sign of friction as the two sides attempt to implement Trump and Kim Jong Un's pledge in June to "work toward complete denuclearization of the Korean Peninsula". "It sets a milestone for other compensation lawsuits filed by Koreans against Japanese entities", said the plaintiffs' attorney Kim Sae-eun.
The elderly men lodged a damages suit against the Japanese firm in Korea in 2005 after they lost a similar litigation in Japan.
In Tuesday's ruling, the top court retained these adjudications.
Meeting with his South Korean counterpart in Seoul, Stephen Biegun said that Washington and Seoul have a shared goal of ending seven decades of hostility on the Korean Peninsula. At that time, the court sent back such compensation cases, including Nippon Steel's case, to Seoul High Court.
The final ruling by the Supreme Court, however, has been delayed amid allegations that the previous government of impeached President Park Geun-hye demanded the delay on concern about frayed ties between Seoul and Tokyo.
The ruling will also change how Seoul handles Tokyo's comfort women scandal, where Japanese Imperial soldiers forced almost 400,000 Korean, Chinese, and Filipino women into prostitution, causing further tensions after Japan funded the Reconciliation and Healing Foundation for victims.
The Japanese company said the ruling was "deeply regrettable".
The Supreme Court's ruling on Tuesday came five years and two months after it received the case.