Seoul, South Korea - For the United States and its geopolitical goals in East Asia, few scenarios would be better than a trilateral alliance with Japan and South Korea that could keep China in check and contain nuclear-armed North Korea.

But plans for a united front continue to buckle under the weight of South Korea and Japan's bitter shared history, analysts say, strengthening Beijing's hand in the region and threatening efforts to rein in Pyongyang's nuclear programme before a second summit between US President Donald Trump and the North's leader, Kim Jong Un.

Relations between Seoul and Tokyo have remained icy since Japan's 1910-45 colonisation of the Korean Peninsula.

In recent months, the two sides have also been sparring over a military confrontation off the Korean Peninsula amid ongoing debates over Japan's treatment of forced Korean labourers and its abuse of "comfort women" - a Japanese euphemism for girls and women forced into prostitution - during World War II.

190110044945076

"The US has been trying to promote trilateral cooperation including South Korea and Japan," said Ryu Yongwook, a professor of international relations at the National University of Singapore.

"But the progressives in South Korea and the conservatives in Japan cannot be genuine friends."

Radar spat

On Monday, Japanese Prime Minister Shinzo Abe omitted the usual mention of South Korea in his annual policy address, focussing instead on improving ties with Beijing and Pyongyang.

The speech followed Japanese allegations that a South Korean warship in December used its fire-lock radar on one of its patrol jets. Seoul denied the claim, and the issue has been snowballing since, with Seoul accusing Tokyo of making multiple aggressive fly-bys of its navy.

Both countries have uploaded videos to YouTube to back their claims.

Few are surprised by what Ryu called the recent "childish fight" between the two neighbours given their bitter past.

"But it's not going to go away," added Ryu, noting that decades-old grievances between the two US allies seem impossible to reconcile.

In November, a Seoul court angered Tokyo after ruling that forced labourers had the right to sue Japanese companies for compensation. Tokyo insists the issue was settled under a treaty signed in 1965.

Meanwhile, a 2015 deal addressing the issue of "comfort women" signed by both countries also unravelled last year after Seoul announced it would dissolve a foundation funded by Japan, essentially quashing what it called a "flawed" agreement.

170127120244979

Japanese officials are now complaining of so-called "Korea fatigue", as issues between the two sides continue to present stumbling blocks to progress, said Tetsuo Kotani, a senior fellow at the Japan Institute of International Affairs.

For the US, managing an alliance alongside two countries with such sensitive histories has never been easy. But past US administrations at least realised the value in creating a united front in the region to counter perceived threats from North Korea and China.

"During an earlier South Korean-Japanese dispute, the Obama administration quietly but quite firmly played a mediator role behind the scenes, sending strong messages to both Tokyo and Seoul," said Bruce Klingner of The Heritage Foundation in Washington, DC.

But under Barack Obama's successor, interest seems to be waning, according to some analysts.

Trump's "America First" approach and treatment of allies has "created distrust in the US role in South Korea and Japan", said Sangsoo Lee, head of the Korea Center at the Institute for Security and Development Policy.

Former Secretary of Defense James Mattis said that Trump's treatment of US allies was a key reason behind his sudden resignation in December. An ongoing tussle over getting South Korea to pay more for military cost-sharing is also raising fears about US troops withdrawing from the peninsula.





In the absence of a united policy front on North Korea and other security concerns, leaders in the region may be eyeing a future in East Asia where the US plays a less prominent role, analysts say.

In his address on Monday, Japan's Abe spoke of taking matters on North Korea into his own hands by meeting Kim directly to address their diplomatic troubles.

South Korean President Moon Jae-in, who met Kim three times last year, has also been acting quickly to improve ties with North Korea, despite calls by the US to move in step with denuclearisation. Moon may have hurt US trust when he called on leaders in Europe to ease sanctions on North Korea last October, which European officials brushed aside.

With a second summit between Trump and Kim in the wings, the US's splintering alliance is "not going to help" their efforts to negotiate with North Korea, Ryu noted. It's also "not going to hurt Beijing's interest", either, if the three-way alliance shows signs of crumbling instead of presenting a united front.

But some analysts expect that the three sides will see the importance of keeping this alliance together, difficult as it may be.

This week, observers speculated that US Ambassador to South Korea Harry Harris may have broached the topic of friction between Seoul and Tokyo with officials in Seoul at a meeting on Monday, but this has not been confirmed.

"These two countries need to cooperate on security issues such as the North Korean nuclear issue and the rise of China as potential security concern," said Ryu.

"In near future, both South Korea and Japan will come together and put these minor issues on the sideline and at least find a semblance of cooperation."