As strategic tensions have mounted in Asia this year, it has become steadily clearer that small and middle powers in the region - countries like Singapore and Australia - face a stark choice. But it is not, as some people suggest, a simple choice between accommodating China's growing power or resisting it.

It is a much more complex choice about how far to support America, as it pushes back against China's increasingly assertive regional conduct, or instead to step back and leave America to confront China's challenge alone.

None of us in these countries want to live under China's shadow. But few, if any, believe that we can avoid making some kind of accommodation with China's growing power and ambition. Whether we like it or not, these are realities which we cannot ignore. We accept that one way or another, China is going to take on a bigger and bigger leadership role in Asia.

At the same time, all of us want America to stay engaged in Asia, to help balance China's power and set limits on how far its regional leadership develops. We look to America to ensure that by accommodating some of China's ambitions, we do not end up submitting to its hegemony.

Our problem is that America sees China's challenge very differently from the way we in Asia do. For most people in Washington, any serious accommodation of China's ambitions is unthinkable. And those few who do advocate accommodation seriously underestimate how far it would have to go to meet even the most modest of China's ambitions.

EQUALS IN REGIONAL LEADERSHIP?

Former Australian prime minister Kevin Rudd, in a report he prepared for Harvard University last year, probably came closest to a realistic estimate of the steps that America would need to be willing to take if a mutual accommodation with China about their respective roles in Asia were to be created.

But even he stopped short of acknowledging the truly essential point: that the only basis for a stable and sustainable relationship between the world's two most powerful states must be based on a mutual sense of parity between them. America must treat China as an equal power, with an equal share in regional leadership.

To most of us in Asia, this seems self-evident. Few, if any, of the region's leaders or foreign policy elites welcome it, because they understand how much we have all benefited from America's leadership of Asia since the 1970s. But they recognise that China's rise is simply too big to ignore. Asia cannot be transformed economically without major changes to the way it works strategically and politically.

That is the reality that Washington has yet to accept. Instead, the assumption there remains that the only possible goal of United States policy in Asia is to keep America's regional primacy essentially unchanged, and that is what US President Barack Obama's "pivot" to Asia aims to do.

And how is the pivot supposed to work? The underlying logic of the policy is simple. It assumes that China can be persuaded to abandon its challenge to US leadership in Asia by concerted regional diplomatic pressure, backed by equivocal threats to use armed force if that pressure fails.

For the past 18 months, America has been using the South China Sea dispute as the issue around which to rally regional opposition to China's assertiveness and to warn Beijing of the risk of military confrontation.

The hope is that if the rest of the countries in Asia support America in demanding that China return to its former acceptance of US regional primacy, and if the Chinese sense that there is even the remotest chance that otherwise it will face a military clash with America, then Beijing will back off.

The appeal of this approach is clear. Diplomatic posturing is cheap, and so is military posturing. If that is all that is needed to preserve US leadership in Asia, then the price is clearly worth it, both for America and for its Asian friends and allies. But its limitations are even clearer. The kind of actions which carry little cost or risk for America and its supporters impose equally small costs and risks on China.

DETERMINED CHINA, DIVIDED AMERICA

Beijing is not reckless in its pursuit of a large regional role, but it is very determined. This is a central part of President Xi Jinping's vision for China, and it seems to be shared by the vast majority of his people. He and they will not be deterred by empty gestures. So America and its friends will only deter Chinese assertiveness by taking actions that impose very real costs on China, and any such action inevitably imposes equally severe costs and risks on America and its supporters.

In fact, the combination of America's uncompromising objectives with the kind of half-hearted practical measures we have seen so far from the pivot could turn out to be the worst possible approach to China's assertiveness. The US refusal to accommodate convinces Beijing that it must push hard to win the bigger regional role it seeks, while Washington's reluctance to do more than talk tough emboldens China to believe that it can push hard without paying real costs.

So far no one in Washington seems to have faced up to this. So while US policymakers and analysts remain committed to perpetuating US leadership in Asia, they are not willing to seriously discuss what would be needed to achieve it. And they keep assuring their friends and allies in Asia that they can support America to effectively resist China's ambitions without seriously damaging their own relations with China.

That is most unlikely to be true, which leaves countries like Australia, Singapore and others in a very difficult position. We are keen for America to stay engaged in Asia, but we are reluctant to support the current policy with its combination of excessive aims and inadequate means. Nor do we want to encourage America to ramp up the kind of pressure that would be needed to force China to back off and accept the old status quo, because we fear that would lead to confrontation and conflict.

But equally, we worry that if we do not support Washington's current approach, and leave it trying to deal with China unsupported, America might start, slowly but surely, to withdraw from Asia. This is no longer unthinkable, whoever wins in November. No one watching this year's presidential election, and the fate of highly symbolic measures like the Trans-Pacific Partnership, could mistake the yawning gap that has opened up between America's policy elites with their commitment to a global role and the majority of Americans on both sides who are very sceptical of it.

So there is our choice. Do we in Asia support a very flawed American policy that offers little hope of a stable future US-China relationship as the foundation of regional order in Asia? Or do we fail to support it, and risk American withdrawal from any major strategic role in the region? Or is there a third option - to start a really frank discussion with Washington about how we see things in Asia and what approach we would really like America to take?

The writer is professor of strategic studies at the Australian National University in Canberra.