Lee Jong-Wha worries that the dispute between Japan and South Korea, both key US allies in East Asia, threatens to change long-standing economic and strategic structures in the region. If Seoul and Tokyo do not improve their bilateral relations, it will weaken their trilateral cooperation with Washington, allowing Beijing to boost its influence in areas – economy, technology and security – that are crucial to their relations with the US.

The author says, although both Japan and South Korea have long been “well-consolidated” democracies, historical grievances and territorial disputes have consistently come back to haunt two of Asia’s largest economies, putting a strain on their relationship. Today their relations “may be at its lowest point since diplomatic ties were established in 1965.” Simmering bitterness over the Japanese occupation from 1910 to 1945 bubbled up again with a row over the issue of the South Korean women who became “comfort women” (sex slaves).

The current dispute began after the South Korean supreme court ruled last year that workers were entitled to compensation from Japanese firms for their forced labour during the war. Tokyo was furious, accusing Seoul of reneging on a bilateral agreement which gave South Korea an economic aid package worth $500 million as final compensation and settlement of historical grievances when the countries restored their diplomatic relations in 1965.

Seoul believed Tokyo had not done enough to address its colonial past and said the deal should not prevent individual victims from suing. Tensions had since escalated into tit-for-tat measures fueled by nationalist sentiment in both countries. The deeply emotional dispute led to consumer boycott that have affected South Korea’s electronics industry, Japan’s consumer goods, tourism and more.

In July, Japan put sanctions on chemicals essential to South Korea’s electronics industry, before removing Seoul from its “whitelist” of trusted trading partners, citing security issues. South Korea then took Japan off its own list. The removals essentially have complicated trade between two closely intertwined economies.

But Seoul’s decision to scrap the General Security of Military Information Agreement (GSOMIA), an intelligence-sharing pact signed in 2016 in the face of a growing threat from North Korea’s nuclear weapons progreamme, alarmed the US. The author says, “China is already seizing the opportunity created by the Japan-South Korea rift to expand its influence, including by playing the role of mediator.”

In fact, Seoul’s decision came just a day after both nations’ foreign ministers met at a trilateral event in late August, where they agreed to keep talking but did not announce any progress in the dispute. China, their host, “encouraged Japan and South Korea to engage in continuous dialogue to resolve their differences.”

The US would have the “best chance” to intervene, “convincing” Prime Minister Shinzo Abe and President Moon Jae-in that the dispute is not in the interests of either side. Some critics said Trump should have acted more forcefully, urging Abe, who has adopted a hard-line stance against South Korea, to try to find a way to ease the tensions for the sake of regional peace and stability.

As usual Trump adopts a “largely hands-off approach” to the dispute. He has merely economic interests in mind when dealing with US allies abroad. He puts American policy up for sale – stoking tensions in their backyard, while urging them to buy US weapons to defend themselves against real or perceived threats. Under the Obama administration, there were signs of thaw as he brought South Korea and Japan to the table in an effort of seeking a unified front in dealing with a nuclear North Korea, and a rising China.

It is only American leadership that can bring the parties together. Now Japan and South Korea must realise the “danger their dispute poses,” it is time for them to exercise “self-restraint” and get their act together – with or without the US – before the dispute spirals out of control.