President Bush’s trip to China has been on his calendar since he took office last January. The agenda for the Asia-Pacific Economic Cooperation forum has changed dramatically in the last month – talk won’t be of trade but of terrorism.

The tone has undergone a remarkable shift as well. The president who once talked openly of China as a strategic competitor and who was baptized in foreign affairs by the infamous surveillance plane incident last spring, now envisions China as a strategic partner. The Chinese have undergone similar transformation. A common enemy provides them a rare opportunity to rebuild their relationship with the United States.

China can be an important member of any global coalition against terrorism. Its immediate value is a 54-mile border with Afghanistan, a narrow corridor that will be of great military value should a protracted ground war be necessary. Beyond that, a new alliance between the United States and China – and, for that matter, Russia – will send a powerful message to states that sponsor terrorism that the old Cold War gambit of playing the superpowers against each other no longer works.

For China, this new alliance is not a spur-of-the-moment reaction to the attacks of Sept. 11; it is part of a bold foreign policy transformation from looking inward to seeing itself as Asia’s economic, military and political leader. Last year, China led the creation of a regional pact against terrorism and drug-running, it extended intelligence services to several of the former Soviet republics in Central Asia, it even indicated interest in the previously unthinkable – joint military operations.

For the United States, this opening offers both great potential and peril. Nowhere is the line between terrorism and fighting for freedom (such as Tibet) more blurred than in China, the religious persecution there is ecumenical, ranging from the Falun Gong to Christians to the Muslims of the Uighur province. The global coalition’s message that this is a war on terrorism, not on Islam, is muddied considerably by China’s membership and its past practices.

The diplomatic task facing Mr. Bush in Shanghai is multiplied by the conferees. Among them will be the new president of Indonesia, Megawati Sukarnoputri, leader of the world’s most populous Muslim nation, a nation that is both alarmed by China’s assertions of regional supremacy and in turmoil over the U.S.-British air campaign against Afghanistan. Taiwan is as suspicious of China as Vietnam is of the United States, Malaysia – also with a huge Muslim population – is as critical of the military campaign against the Taliban as Australia is eager to join in.

This non-economic economic summit will severely test the two pillars upon which the administration’s global anti-terrorism coalition stands. The extent to which every country will be free to define its role in that coalition could determine whether Indonesia and Malaysia participate or are thrown into revolution. Making the distinction between terrorism and legitimate dissent is China’s challenge.