Beijing says that the United States is stoking Taiwan's moves towards independence by selling the island advanced weapons. Washington insists that the arms are for self-defence, in the face of a threatening Chinese military buildup.
Mainland China may be as much as a generation behind the US in terms of naval power. But within the next few years, its naval modernisation and expansion programme will probably enable it to launch a successful amphibious invasion of Taiwan, should the island attempt to seek formal independence. And by then, Beijing will have the air power to protect its ships as they cross the Taiwan Strait.
The naval buildup will also help to make it the dominant regional power in the South China Sea, able to enforce its sovereignty and maritime boundary claims against other rivals, including Vietnam, Malaysia and the Philippines. This is one reason why all Southeast Asian states back Beijing's 'one China' policy. They want to keep the situation calm because they know that mainland patriotic fervour to recover Taiwan feeds Chinese irredentist claims elsewhere.
But the crisis Southeast Asia fears most would be one between Beijing and Washington over Taiwan. The last thing Southeast Asian countries want is for regional stability to be disrupted and economic growth undermined by a conflict in which they would be under intense pressure to choose sides between these two big powers. Southeast Asia's interest lies in having good relations with both, and balancing one against the other to avoid being dominated by either.
Still, both mainland China and the US have developed substantial common interests in maintaining cross-strait peace. Their mutual trade and economic dependence are already large, and likely to intensify. If a conflict with the mainland was provoked by nationalists in Taiwan, it is far from certain that the US would feel bound to intervene militarily. However, if an armed conflict did erupt over Taiwan, it could escalate. Would Washington try to impose a maritime embargo on Beijing and cut its vital energy and other seaborne imports in, or close to, the Southeast Asian straits? Probably not, short of all-out war, which could be catastrophic for both Beijing and the US, and for Asia as a whole, especially if nuclear weapons were unleashed. Moreover, an embargo would be difficult to implement and would affect the vital trading interests of other East Asian countries that Washington would want on its side.
But one thing is clear: if China continues to grow at anything like the rate of recent years, it will become increasingly dependent on imports of oil and gas.