EVER since US President Barack Obama announced his "pivot to Asia" in 2011, doubts have been growing on both sides of the Pacific about whether he is really serious about it. Last week, he came to Asia to quash those doubts. Mr Obama wanted to reaffirm once and for all that he is determined to preserve America's leadership in Asia, and defend that leadership against a growing challenge from China.
That is why he stood beside Japan's Prime Minister Shinzo Abe to declare that America would help Japan defend the disputed Senkaku/Diaoyu islands. It is also why he strongly reinforced US strategic commitments to the Philippines. These were very big and important steps for the US President, steps which Mr Obama has until now clearly been very reluctant to take. He took them because there was no other way to quash the doubts and restore the credibility of his Asia policy, and indeed his entire foreign policy.
It is not hard to see why doubts about the pivot have arisen. It has always been hard for Mr Obama and his team to show that they are fulfilling the pivot's promise to swing American power to Asia. They have been distracted by major problems at home. Their attention has been repeatedly drawn away from Asia by crises in the Middle East and, most recently, in Europe.
Moreover, America's responses to those crises have raised questions about whether Washington really has the resolve to play the leadership role it claims for itself, whether in Asia or elsewhere. Mr Obama's weak and muddled responses on Syria, as well as his very cautious approach to the crisis in Ukraine, have suggested that he, and America in general, are increasingly reluctant to meet the demands of global primacy.
Those doubts have also been reinforced by events in Asia since the pivot was announced. From early 2012, Beijing has staged a series of seemingly deliberate tests of US resolve. It has escalated pressure, including military pressure, against US allies over disputed maritime territory. It has done that to test whether Mr Obama is prepared to risk a military clash with China by defending the interests of its allies in those disputes.
Until last week, the US President was seen to fail these tests. In 2012, he did nothing concrete to stop China from taking control of Scarborough Shoal from the Philippines, and he deliberately avoided making any clear commitment to support Japan militarily in the event of a clash with China over the Senkaku/Diaoyu islands. More junior US officials, meanwhile, sent mixed signals.
This timid response to China's increasingly assertive diplomacy has given a clear impression that, despite the "pivot" rhetoric, America has indeed been stepping back from leadership in Asia as China's power grows. After all, US leadership is based on its alliances in Asia, and those alliances are based on the confidence of its allies that America will stand up for them against China. If that confidence wanes, so does America's regional leadership.
Washington has tried to divert attention away from this awkward reality by shifting the focus of the pivot to economic questions. US leaders have taken to saying the pivot is as much or more about economics and trade as it is about politics and strategy. In doing so, they have made the Trans-Pacific Partnership (TPP) the cornerstone of the President's Asia policy.
But the TPP is in deep trouble, not just because it is proving hard to negotiate with the other international parties, but also because it is regarded with great suspicion in Congress. Mr Obama is not going to be able to build a new foundation for US leadership in Asia on the basis of a trade deal which will never get past the Senate.
So if Mr Obama was serious about maintaining the status quo in Asia and preserving US regional leadership, he had no option but to make the unambiguous strategic commitments that he made in Asia last week. But that is not the end of the story. The big question now is how will China respond.
If the US President's bold words deter Beijing from putting pressure on Washington's allies and impel it instead to back down over its territorial disputes with Tokyo and Manila, then Mr Obama's diplomacy will have been a success. But what if Beijing calls Mr Obama's bluff? How will he react if, instead of pulling back, China continues to use its armed forces to press territorial claims against the Philippines and Japan? Above all, what will Washington do if Chinese and Japanese forces do one day clash in the East China Sea? This would present Mr Obama with an appalling choice. If, after his bold statements last week, he then failed to support Japan, US credibility in Asia and beyond would be shredded, the future of the US-Japan alliance would be endangered, and US claims to leadership in Asia would be dealt an immense blow.
But what if he did send US forces to Japan into a conflict with China? Where would that lead? Mr Obama must have thought about this, and he must realise what a dangerous step this would be. Economically, such a conflict would be catastrophic. Militarily, it could be even worse. The simple fact is that America has no sure military options to win a conflict with China in the East China Sea, and no way to ensure that such a conflict would not escalate to a full-scale war, including, conceivably, a nuclear war.
America simply cannot assume that China would step back and accept a humiliating backdown to avoid escalation, so any move to conflict carries the real risk that America itself would have to face that terrible choice. That is why he has been so reluctant to make commitments to Japan and the Philippines until now.
The US President's statements last week have not solved his policy problems in Asia. They have only deepened them. Mr Obama, and America, still have to find a way to build a stable, secure, durable relationship with a powerful and ambitious China. Trying to force China into accepting US primacy in Asia is not the way to do it. If America is going to stay in Asia, it will either have to share power with China, or confront it as an adversary.
The writer is a professor of strategic studies at the Australian National University. His book The China Choice: Why We Should Share Power was published last year by Oxford University Press.