FILE- In this July 6, 2017, file photo, U.S. President Donald Trump poses with Japan's Prime Minister Shinzo Abe, right, and South Korea's President Moon Jae-in, left, for a photo before the Northeast Asia Security dinner at the US Consulate General Hamburg, in Hamburg, Germany. Japan and South Korea share long-term uncertainties about their alliances with a less-engaging United States, a shift highlighted by Trump’s “America first” approach to the world and complaints about the costs of stationing some 80,000 U.S. troops in South Korea and Japan. (AP Photo/Evan Vucci, File)

SEOUL, Korea, Republic Of - It took a bombshell resignation before Japanese Prime Minister Shinzo Abe heard anything nice from South Korea.

The rare praise came after years of diplomatic rows and testy confrontations between Abe and South Korean President Moon Jae-in, and only after the Japanese prime minister said last month he would leave office after eight years because of ill health.

With Abe and Moon in charge, the relationship between the key U.S. allies sank to new lows, with grievances over wartime history spilling over into trade and military issues. Japan's political shakeup could be an opportunity for South Korea, which sees Abe’s departure as a chance to clear things up between the rivals.

Senior South Korean officials during a recent national security council meeting vowed to “advance stalled negotiations on pending issues” once a new Japanese leader is in place. Yoshihide Suga, who was chief Cabinet secretary and Abe’s right-hand man, won Japan’s governing party leadership vote Monday, virtually guaranteeing parliament will choose him as the next prime minister.

Suga has also hinted at improving ties with South Korea.

“China and South Korea are neighbours, and even though there are difficult problems between us, I plan to pursue diplomacy that can allow us to always communicate and develop strategic relations with them, rather than choosing one or the other,” he said in a recent debate.

Good relations are crucial to both Japan and South Korea.

Despite their political conflicts, they remain closely connected economically and face similar challenges. Those include North Korea's growing nuclear arsenal and a rising authoritarian superpower in China.

They also share long-term uncertainties about their alliances with a less-engaging United States, a shift highlighted by President Donald Trump’s “America first” approach and his complaints about the costs of stationing some 80,000 U.S. troops in South Korea and Japan.

“Patching up differences with Tokyo would improve alliance co-ordination with the United States, help manage regional uncertainties concerning China, and provide Seoul leverage in dealing with North Korea,” said Leif-Eric Easley, a professor at Ewha University in Seoul.

What remains unclear, however, is whether Abe’s exit will prove to be a diplomatic turning point. Mutual resentment runs deep and goes beyond individual politicians.

To South Koreans, Abe was less likable than even North Korean leader Kim Jong Un, according to a November Gallup Korea poll. Abe was often seen in South Korea as a right-wing nationalist intent on whitewashing Japanese colonialism and atrocities on the Korean Peninsula before the end of World War II.

Placing the blame for bad relations entirely on Abe, however, overlooks the broad public support he won at home for a tough policy toward South Korea.

There’s a widespread view in Japan that South Korea is violating international norms by repeatedly revisiting wartime issues that were supposed to have been settled, said Choi Eun-mi, a Japan expert at South Korea’s Asan Institute for Policy Studies.

“Abe’s resignation does offer a window for improved relations, but it’s unrealistic to expect significant changes,” she said.

There will be chances to resume stalled talks between the countries' leaders, including a possible three-way summit with China that South Korea hopes to host in November. But it will take longer for Seoul and Tokyo to “rediscover their importance to each other” beyond their interdependence in security and co-operation matters with Washington, Choi said.

South Korea and Japan have long differed over history, but previous political tensions were softened by vibrant trade and exchanges of pop culture and tourism.

That wasn’t the case in 2019 when Japan’s move to place export controls on chemicals vital to South Korea’s semiconductor industry sparked an outpouring of national anger in South Korea and sweeping boycotts of Japanese products.

Moon accused Abe’s government of weaponizing trade to retaliate against South Korean Supreme Court rulings in 2018 that ordered Japanese companies to offer reparations to aging Korean plaintiffs who had been forced into wartime slave labour.

Seoul later threatened to terminate a military intelligence-sharing agreement with Tokyo, a major symbol of their trilateral security co-operation with Washington. It eventually backed off after being pressured by the Trump administration, which until then seemed content to let its allies escalate their feud in public.

South Korea and Japan’s strained relations have hurt their ability to deal with the unpredictable foreign policy of Trump, who has questioned the value of U.S. alliances while raising tensions with China, a major trading partner for both, said Park Won-gon, a professor at South Korea’s Handong University.

“Ideally, strong co-ordination between South Korea and Japan would help steer the Trump administration into pursuing its regional strategies within international norms and rules,” Park said.

South Korea will likely need to close the gap between its domestic court rulings and existing bilateral agreements to improve ties with Japan.

Many Japanese see the South Korean forced labour rulings as a challenge to a 1965 treaty between the countries that was accompanied by Japanese payments to restore diplomatic ties. Tokyo insists that all compensation matters were settled then.

There’s also frustration over Moon’s 2017 decision to walk back a 2015 agreement negotiated under South Korea's previous conservative government that attempted to “irreversibly” resolve a decades-long impasse over Korean women forced into sexual slavery by Japan’s wartime military.

The deal, which had Japan give $9 million to a foundation to help the victims, sparked huge protests in South Korea, where many accused their government of settling for far too little after failing to consult victims. There were claims that Abe was attempting to silence the women with money.

There has been little sign that either government is willing to budge.

Moon continues to demand Japanese respect for the South Korean court rulings. Suga, who is likely to be named prime minister later Wednesday, has pledged to inherit Abe's policies and push them forward.

There's a further complicating possibility that South Korean courts may order the liquidation of local assets of Japanese companies that have refused to compensate forced labourers.

A breakthrough may have to come from legislation, but that won’t be easy, either.

Former South Korean National Assembly Speaker Moon Hee-sang last year proposed a foundation created by private donations from both countries to compensate forced labourers. The bill, which eventually died, was heavily criticized by lawyers and activists representing victims, who said the foundation would sidestep the Japanese government’s direct responsibility.

“Regardless of who becomes Japan’s next prime minister ... there will be limits to how much bilateral relations can improve unless the countries find a solution to the forced labour issue,” Park said.

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Kim Tong-hyung has covered South Korea for The Associated Press since 2014.

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AP reporter Mari Yamaguchi in Tokyo contributed to this story.

News from © The Associated Press, 2020