How Asia's geopolitical landscape will evolve over the next couple of decades is not easy to foresee. But it is apparent that an increasingly assertive China is unwittingly reinforcing America's role in Asia as the implicit guarantor of security and stability.

There are at least four possible Asian security scenarios. The first is the rise of a Sino-centric Asia, as desired by Beijing. China seeks a multipolar world but a unipolar Asia. By contrast, the United States desires a unipolar world but a multipolar Asia. A second scenario is of the U.S. remaining Asia's principal security anchor. A third possibility is the emergence of a constellation of Asian states with common interests working together to ensure both power equilibrium and an Asia that is not unipolar. A fourth scenario is of an Asia characterized by several resurgent powers, including Japan, India, Vietnam, Indonesia and a reunified Korea.

Of the four scenarios, the least unlikely is the first one. China's neighbors increasingly are uneasy about its growing power and assertiveness. While Beijing aspires to shape a Sino-centric Asia, its actions hardly make it a credible candidate for Asian leadership.