The standoff between China and the Philippines in the South China Sea has evolved over the last five weeks into a bizarre brinkmanship triangle. The United States finds itself reluctantly backed into corner number three: this is definitely not the pivot to Asia that Washington had in mind.

The beauty of brinkmanship, of course, is that actually going over the brink is seldom required. Most likely it won’t be necessary in this situation either. Despite some tough talk from both Beijing and Manila, the hope now is that the two-and-a-half-month fishing moratorium due to be imposed by China on May 16, imposed annually since 1999, will finally help to douse a few tempers, and bring the confrontation to a peaceful conclusion.

The U.S. government must be praying for such an outcome. If the Chinese and Philippine crews glowering at one another over the contested Scarborough Shoal actually start shooting, the ensuing conflict is likely to pan out in one of two directions:

Scenario A: China’s superior navy initially makes short work of the Philippine opposition, but Manila then invokes its Mutual Defense Treaty with the United States. Honoring its treaty obligations, the U.S. dispatches a carrier battle group to the South China Sea and reclaims the contested Scarborough Shoal on behalf of its Philippine allies.

Scenario B: As China swiftly takes Scarborough Shoal by force, Manila invokes its Mutual Defense Treaty with the United States. But Washington doesn’t pick up the phone, maintaining sheepishly at subsequent press conferences that these “obscure” maritime territories fall outside the MDT’s confines.

Either policy option is miserable from the U.S. perspective. War with China is obviously something to avoid at all costs. But at the same time the abandonment of the Philippines would torpedo the strategic rebalance to Asia before it has even got underway: Washington’s allies in the Pacific would conclude that the United States is no longer dependable as a hedge against China (which is the reason most East Asian countries want to have the U.S. around).

The Mutual Defense Treaty between the Philippines and the United States is a sixty-year-old anachronism – a throwback to the Cold War days when countries existed in a pre-globalized environment and the benefits of picking sides vastly outweighed the costs.

But the interlinked economies of the 21^st century means there’s no longer a “them and us”: there’s only an “us” (North Korea aside). This is the age of the Free Trade Agreements and the Trans-Pacific Partnership, not the mutual defense pact. So while it’s understandable that Philippine government ministers should want to remind both China and the U.S. of the Mutual Defense Treaty’s existence – because in a confrontation with China it’s the only card they can play – they are no doubt conscious that the feeling in Washington is very far from mutual.

In fact, U.S. support for the Philippines is very much qualified. Brinkmanship is fine: the prospect, however remote, of American intervention could be enough to deter Chinese military action. But go over the brink, Presidente, and you’re on your own.

The U.S. has promised Manila that it will honor its treaty obligations, while effectively assuring China that it will stay out of the dispute. In the event of an armed conflict, these positions become totally incompatible. It would be a horrible dilemma for the Obama administration.

However, China’s calculus is itself anything but straightforward. Chinese naval forces could easily take the contested reefs and probably suffer no American reprisals: but what then? In much of East Asia, China would be portrayed as the villain that opted to whack its weaker neighbor rather than accept a reasonable offer of international arbitration. Countries like Japan, dismayed at American absenteeism, might start to militarize unilaterally, finally convinced that China’s rise is something to resist. And there are further layers of complexity. Military action against the Philippines might just provoke a U.S. response – and bring down on China exactly the kind of humiliation that assertiveness in the South China Sea is meant to banish from history. Equally, the failure to act militarily would only infuriate the army of Chinese netizens who have already declared war on the Philippines a thousand times on Sina Weibo.

This is potentially a critical juncture for both Chinese and U.S. interests in the Pacific region. The Philippines, by far the weakest player in the game of trilateral brinkmanship, arguably has the least to lose.