The shortest voyages carry the richest cargo in the intra-Asia trades. The three high-end trading partners that command these big volumes are China, Japan and South Korea, which together account for 20 per cent of world trade.

Since 2012, they have been working fitfully to leverage their already envious situation into something more. But having the value of the mighty three become greater than the sum of its parts, has not been easy and nor is it anywhere near complete.

At a comparatively minor level, there are territorial disputes in the way - such as China's land grab of the Spratly Islands. Most unhelpful to mutual trust was China's haughty dismissal of the negative ruling handed down by the International Court of Arbitration in the Hague in the Spratly case.

Not that that South China Sea dispute is of material interest to those who trading in East China Sea and the Sea of Japan, but such cavalier attitudes towards international agreements and official dispute resolution mechanism sparked something of a "me-too" attitude about one's right to waive the rules at will.

So while the lingering Korean-Japanese dispute over jurisdication of the 46-acre Liancourt Rocks tends cloud an air of trust that might otherwise reign among the trading partners, this has since been augmented by other allegations of wrongdoing that sour the mood.

At issue today is a willingness to break agreements that would make trade accords immune from issues unrelated political disputes.

Given these simmering tensions little substantial trilateral work has been done, and what few accomplishments there have been focus on more easily harvested "low-hanging fruit", issues upon which agreement is more easily secured.

Such is the work of the joint Trilateral Cooperation Secretariat and the ministerial meetings it organises. First proposed in 2002, the object of the TCS is and was to formulate a China-Japan-South Korea Free Trade Agreement at a time when trade among them totalled US$690 billion. After exploratory talks, Intersessional Meetings of the Negotiations on Free Trade Agreement (FTA) among Japan, China and Korea in Tokyo became more firmly entrenched in 2014.

But the road has been bumpy and fraught with emotion. Historical issues that helped bring acrimonious ends trilateral summits after 2012 were barely mentioned in joint declarations. The only reference to history was that all three sides agree to carry out further cooperation “in the spirit of facing history squarely and advancing towards the future.” This is a common refrain that combines China and South Korea’s insistence that Japan express greater contrition for its behaviour in the 1930s and '40s while Japan resisted and insisted on a more future-focused outlook.

Outside of North Korea, no other regional flashpoints - such as the South China Sea issue - made it into the joint declaration. Instead, the parties limited discussion to consultations on counterterrorism and cyber issues and “low-level” security.

On security, North Korea topped the agenda with all reaffirming "opposition to the development of nuclear weapons on the Korean Peninsula” in line with UN Security Council resolutions together with a commitment to “continue our joint efforts to resume meaningful Six Party [China, Japan, North Korea, Russia, South Korea and the US] Talks at an early date”.

They all agreed to continue work toward economic integration by making “further efforts toward the acceleration of the trilateral FTA negotiations”. There are also plans for a wealth of trilateral ministerial meetings to advance economic ties and market integration in specific areas. In short very little progress was made in establishing an FTA.

"All in all, the trilateral summit was exactly what observers expected - a mostly anodyne [inoffensive] dialogue without attempting to untangle the historical and territorial issues that act as wedges," noted Japan's Diplomat magazine. "Given that this summit hadn’t been held in three years, even getting [Japanese Premier Shinzo] Abe, [Chinese Premier] Li [Keqiang] and [South Korean President] Park [Geun-hye] in the same room was an accomplishment."

The North Korean situation has again impeded progress developing trade relations with US President's Donald Trump's more aggressive policy. China has been a fitful partner in efforts to end North Korea's nuclear arms programme. While it agrees that it should end, Beijing is against the US enhancing its role and reputation in the Asia-Pacific region.

The current stumbling block is the new US missile system called THAAD (Terminal High-Altitude Area Defence, ie, anti-missile missile batteries), which "threatens" China in much the same way "Star Wars" (aka the Strategic Defence Intiative) "threatened" the Soviet Union in the 1980s. The threat is entirely defensive yet real, leaving one party relatively immune from attack while the other's attack capability is fully intact, like having one gunslinger with no effective gun while his rival is fully armed.

China objects to Korea allowing THAAD on its soil, but instead of fighting this diplomatically, as it has pledged to do - it uses trade as a diplomatic weapon, Koreans allege.

So when Chinese Premier Li calls for speeding up negotiations of China-Japan-South Korea free trade agreement (FTA) as he does from time to time, the other parties, particularly those in South Korea look on incredulously.

He may say "China stands ready to work with relevant parties to speed up negotiations of China-Japan-South Korea FTA, taking a more active part in promoting negotiations on the Regional Comprehensive Economic Partnership, so as to achieve the long-term goal of the Free Trade Area of the Asia-Pacific (FTAAP)," but South Koreans may be forgiven if they doubt his sincerity.

"This has reinforced the perception that Beijing cannot be expected to abide by international norms, such as the separation of politics from economic affairs, when it feels the need to advance or defend its interests," said editorialist Kim Kyung-ho in the Korean Herald.

In response to the installation of the anti missile missile batteries, China ordered Korean retail giant Lotte to shut 74 of its 112 outlets on the mainland for violations of safety, sanitary and environmental regulations - rules that did not apply to other chains.

Lotte has said it suffered losses of KRW500 billion (US$442 million) over six months, making only seven per cent of the revenue it made in the same period in 2016.

Korea's Hyundai Motor saw its Chinese sales in the first seven months of 2017 decline 40 per cent to 351,292 units. Its factories in China were recently compelled to stop operations for days as local suppliers suspended parts delivery due to delayed payments.

Hyundai Motor has been restricted from remitting cash from here to Beijing Hyundai Motor, a 50:50 joint venture with a Chinese state-owned firm, to ease its financial crunch, said the Korean newspaper.

BAIC Motor, the Chinese partner, is pressuring Hyundai Motor to change parts suppliers to local ones to reduce production costs.

Beijing has also excluded electric vehicles equipped with Korean-made batteries from its subsidy schemes.

Such restraints on Korean companies run counter to the provisions of the trade accord, says Seoul, which adds that it supposedly has most favoured-nation status and is guaranteed nondiscrimination by China in its local business dealings.

China can also be deemed to have disregarded the free trade deal by imposing an unofficial ban on group tours to Korea and banning the country’s pop artists and cultural contents from entering the Chinese market.

All this has brought about rising discontent in the Korean business world because Seoul is shy to avail itself of the dispute resolution measures it could take under the bilateral FTA it has with China for fear of bringing on further retaliation.

 “China’s retaliation regarding the THAAD deployment is an issue that should be dealt with on the government level,” said an official at a Korean business association, requesting not to be named.

 “But the [South Korean] government has so far prodded companies to work out responsive measures on their own,” he said.

Most restraints on Korean companies may be taken to the process of investor-state dispute settlement, as stipulated in the trade accord. But experts say it would carry too much risk for Hyundai, Lotte and other Korean firms to sue the Chinese government.

Given the riches of this trade, and the need for these three nations to trade with each other, one may ask how necessary are formal trade accords at a time when all levers of power are pushed and pulled regardless of previous agreements and regardless of who's ox is being gored in international trade.