is a professor of law and a member of the faculty of the Center for East Asian Studies at the University of Pennsylvania

When hordes of athletes, dignitaries, journalists and tourists arrive in Beijing for the Olympics, they will find a China that has become strong and prosperous to an extent unimaginable a generation ago. The quest for wealth and power, an ancient imperative of Chinese statecraft, has been a central goal of China's Communist leaders. They have pursued it through Soviet-style economic planning, to catastrophic Maoist "leaps forward," and, more recently, "Wild East" capitalism.

China's rulers are eager, indeed, anxious, to press this image of a rich and formidable China upon visitors to the Games and upon the wider world. The host regime sees the Olympics as a coming-out party for a recently minted great power, as well as a final step in China's recovery from the criticism that followed suppression of the Tiananmen Movement in 1989 and helped scuttle Beijing's bid for the 2000 Games.

Yet China is unusual for a rising power. More than the United States or the Soviet Union or Great Britain during their periods of ascension, China is still weak. Despite a massive military modernization program, China's capabilities remain limited, especially its ability to project conventional force over distance.

Moreover, China is still poor. True, its economy is now the world's second-largest in "purchasing power parity" terms (a measure that adjusts for lower costs of many goods and services in less developed countries). And China's economy has been growing at more than 10 percent a year for much of the last three decades.

In the more common exchange-rate-based measure of economic size, however, China trails Germany. China's economy is vast, but then, so is its population. Great powers ordinarily do not rank below the world median in per-capita income. But China does. By World Bank measures, it is a lower-middle-income country. Average income does not much surpass $2,000 - or a still-modest $5,400 or so in purchasing power parity terms.

Challenges posed by this relative poverty are made worse by severe inequality and an aging population. By the most common measures, China's society has greater inequality than that of the United States (where inequality is much higher than in almost any other developed economy) and most other countries, especially in East Asia. Chinese urbanites have incomes more than three times those of rural residents. Average income in Shanghai is nearly tenfold that of China's poorest provinces. Policies to redress still-rising inequality are just beginning. If zealously pursued, such policies could threaten the growth that has underpinned China's rise and its rulers' legitimacy.

China also will grow old before it gets rich. Senior citizens are the fastest-growing age group in China. The proportion of Chinese above age 65 soon will approach that in the United States, and it is much higher than in other developing countries. The graying of China stems from harsh population-control policies adopted a quarter-century ago to avoid economically ruinous population growth. But the increasing ratio of retirees to workers imperils investment rates and productivity gains that have sustained China's growing economy and geopolitical clout.

In keeping with its uncertain prowess, China is an ambivalent power. Its approach to foreign relations often still hews to Deng Xiaoping's injunction to "hide brightness and nourish obscurity" - to downplay strength and avoid driving other states to contain or counterbalance China. Under Hu Jintao, China's foreign policy has pursued a "peaceful rise" or "peaceful development" or "harmonious world" - each catchphrase adopted because its predecessor was insufficiently reassuring to an increasingly wary world.

A more aggressive Chinese approach has been emerging. Officials and thinkers are invoking a "Chinese model" developing countries could embrace instead of the neo-liberal economics and trade liberalism preached by Washington. Chinese leaders lecture once-smug Americans on failures of U.S. economic policy.

To some extent, greater assertiveness is inevitable. Rising powers seek to change international regimes they did not shape. China, however, has compelling reasons to accept, even support the status quo for now. It depends on participation in the global economy to sustain growth and stability, and it lacks the leverage to demand major changes. Still, although Chinese leaders have a strong record of putting interest ahead of ideology, there is a risk that China's heady sense of accomplishment and resurgent popular nationalism - both of which will be on display at the Olympics - will drive China to challenge the rules of the game on matters ranging from trade to security. Although acquiescence is more likely in the near term, if and when China becomes less compliant, it could pose problems for another country that benefits even more from the current order - the United States.