The United States-China annual Strategic Security Dialogue has come and gone without any hint of progress on South China Sea issues. Presumably, the two sides will keep talking with a view to reaching some sort of an understanding or compromise perhaps associated with Chinese President Xi Jinping's visit to Washington in September.
However, the situation is not static and there are several "known unknowns" that could affect the South China Sea situation in the foreseeable future.
That phrase, of course, comes from former US defence secretary Donald Rumsfeld's description of threats that has entered the popular lexicon: "There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know."
A significant initial part of the US pivot to Asia is its enhanced alliance with and military presence in the Philippines. The US-Philippines Enhanced Defence Cooperation Agreement (EDCA) gives US troops wide access to local military bases.
But it has been legally challenged as unconstitutional because President Benigno Aquino bypassed the Senate and implemented it with an executive order. If the challenge is upheld by the Philippine Supreme Court, it could undermine the presence and regional impact of US forces "rotating" through the Philippines.
Even if the court ruled that the agreement is constitutional, it might also rule that it needs Senate approval. Whatever the outcome, if the court does not rule before US President Barack Obama's visit to Manila in November, it will raise concerns as to how serious the Philippines is regarding its alliance with the US.
A requirement of Senate approval could also apply to any agreement with Japan to allow its aircraft and naval vessels to use bases in the Philippines.
This would embolden domestic Philippine opposition to a US and Japan military presence and encourage China to continue its assertiveness vis-a- vis the Philippines. US support for the Philippines' stand against China could wane.
However, if the EDCA is upheld, the robustness of the Philippines' opposition to China's assertiveness and the US support for that would be invigorated, as would tensions between China and both.
The Philippines' opposition to China's South China Sea claims and actions has become a personal plank in Mr Aquino's presidency. But his term in office will end in May next year. It is not certain who will replace him and whether he or she will continue his virulent opposition to China's claims and his pro-America policy.
One of the prospective candidates, Mr Aquino's former vice-president Jejoma Binay who recently resigned, is thought to not be as uncompromising on this issue as Mr Aquino.
The new president may try to reduce conflict with China and retard or even reverse increasing defence ties with the US and Japan. This would convince China that its strategy is working and that by standing pat and firm, it can and will persuade the other claimants that it is in their better interest to negotiate with China.
The United Nations Arbitral Tribunal will hold a hearing on the Philippines' suit against China next month. If the tribunal eventually decides that it does not have jurisdiction or that the Philippines has not made a valid legal case, the suit would be terminated. Otherwise it will proceed to a decision, likely next year.
If the panel decides it does not have jurisdiction, realists will crow that "international law is the arms of politics", and that international law is shaped and works in favour of the big powers.
More importantly, the South-east Asian claimants - including besides the Philippines, Brunei, Malaysia and Vietnam - will be resigned to negotiating their overlapping claims with an ever more powerful and intimidating China.
Like the Philippines, they will then probably take political and even military measures to protect themselves - such as drawing ever closer to the US.
If the panel decides it does have jurisdiction and goes on to rule against China's nine-dash line claim, it could be committing institutional suicide. China will not abide by the ruling, legal and political uncertainty will reign in the South China Sea, and violent incidents there are likely to proliferate. The authority and legitimacy of the dispute settlement mechanism and even the Law of the Sea itself may be weakened.
It is thought that in Vietnam, there is a struggle within the leadership for influence between pro-China and pro-US factions.
In January next year, its leadership will change. If a pro-China faction triumphs, Vietnam may well subdue or even settle its maritime jurisdictional issues with China. This would serve as a lesson and example for other claimants and would dampen support for the Philippines' position. If a pro-US faction gains an edge, that might mean stiffened Vietnam opposition to China's claims and actions, and deeper US political inroads in the region.
There are also several factors that could detract from the robustness of the continued US pivot towards the region, such as the competing attention of other world hot spots combined with a change of administrations.
If US interest and staying power wane, the smaller South-east Asian nations may hedge towards China. As Singapore's Foreign Minister K. Shanmugan has said to the US, "you are either in or you are out".
There are other known unknowns like another incident between Chinese defence forces and provocative, probing US intelligence-gathering aircraft and vessels, or a physical clash between military or pseudo-military elements of China and Vietnam or China and the Philippines. Any such incident would alter the situation, sending tensions soaring and international relations spiralling downwards.
These are all known unknowns.
However, it is the unknown unknowns that are more likely to surprise and seriously destabilise the region.
Policymakers surely have their work cut out for them to maintain momentum towards a China-US accommodation in the South China Sea.
This article was first published on June 27, 2015.
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