What in the world is China?

What better way to celebrate a birthday than to take to the world stage? Last week, Hu Jintao became the first Chinese president to address the U.N. General Assembly, a privilege seemingly reserved for the president of the United States and colorful despots such as Moammar Kadafi. The People's Republic, which turns 60 on Thursday, has evolved from tin-pot polity to powerhouse. And among the spectacular transformations China has undergone, its dramatic turnabout in how it relates to the world stands out.

China began as a pariah state, rejected by and immensely hostile toward the world community. Marxism shaped its view of international organizations as the "instruments of capitalist imperialism and hegemonism," and for decades China had little to do with them.

Fast-forward to last week, when Hu proclaimed the "important role" of the United Nations and entreated the international community to "continue our joint endeavor to build a harmonious world of enduring peace and common prosperity."

Today, China has joined every major international organization to which it is eligible and signed more than 300 international treaties. It has even had a hand in creating new regional groups. "They are acting like the new us," a U.S. official told me. They prepare, send huge delegations to summits and carefully cultivate diplomatic capital.

This is not just lip service. In many cases, China's engagement with global entities such as the World Trade Organization and the International Monetary Fund has prompted Beijing to bring its conduct in line with international standards.

The next step, though, is a critical one. Now that China is fully engaged and has earned considerable clout, what will it do? Will it increasingly abide by and support international standards? Could it eventually become a genuine leader for the global common good, with the risk and sacrifice that often entails?

Beijing sends mixed signals. On the hopeful side, we see China's leadership on the North Korean nuclear issue -- hosting many rounds of the six-party talks, producing draft agreements and now, for the first time, enforcing U.N. sanctions against its nominal ally. And although it once objected to the whole idea, China now has 2,000 of its citizens in U.N. peacekeeping operations.