The terror attacks against the World Trade Center and the Pentagon have given the United States and China an opportunity to improve their bilateral relations. Analysts expect to see an improvement in Sino-U.S. ties in the short term, but they say the U.S. anti-terrorism push may produce problems over the longer run.

Relations between Beijing and Washington have been rocky - with deep disagreements on Taiwan, human rights, missile defense and other issues. The relationship took a sharp downturn after the collision earlier this year between a U.S. surveillance plane and a Chinese fighter jet.

But the United States and China have a common interest in stopping terrorism, and China specialist Andrew Nathan says that is likely to bring the two countries closer. "I think in the near term, it will bring an improvement in the U.S.-China relationship. A lot of other issues, and perhaps especially human rights, are going to be given less priority. The notion of China as a threat, which entertained the American public for a number of years back in the [19]90s, I think is going to disappear because now there is a real threat to look at. And China and the U.S. have a definite common interest in opposing terrorism and Islamic fundamentalism that's rooted in central Asia."

In recognition of Islamabad's strong support for the anti-terror campaign, the United States and other countries have rescheduled Pakistan's foreign debt payments.

Mr. Nathan, a political science professor at Columbia University in New York, says he does not know what China may have requested in exchange for its support. "There are some things that they would like," he said. "One is an end to or a drastic reduction in American arms sales to Taiwan. That's very high on their list. There are some limits on American technology sales to China and limits on, for example, the launching of American and western satellites with American technology on Chinese rockets. They would like those limits to be lifted as well."

China specialist John Tkacik with the Heritage Foundation in Washington says the two countries are not going to negotiate the terms of China's participation in the anti-terrorism campaign. "My own feeling," he said, "is that U.S.-China relations probably should not be affected by the terror wars. This is not a negotiating exercise. We're not going to dicker with the Chinese over it. They have a problem. We have a problem. We're going to join and overcome the problem."

Professor Nathan agrees that China and the United States will not engage in actual bargaining, but he says Chinese officials will probably seek opportunities to point out what they see as inconsistencies in U.S. policy. For example, China considers Muslim insurgents in the western region of Xinjiang to be separatists. And he says Beijing sees the Taiwan issue the same way and wants Washington to end its military support for Taiwan."

I think they will try to argue that the American position is inconsistent in the region - that on the one hand, if you're going to get rid of terrorism, you have to have respect for the integrity of states. You can't support separatist movements and that the Taiwanese thing is a separatist movement. So, they will argue that the U.S. should not use a double standard.

Robert Sutter, a China specialist at Georgetown University, says he expects the Taiwan issue to remain a source of tension in Sino-U.S. relations. He does not think increased cooperation on terrorism will change that. "Obviously," he said, "the cooperation on terrorism will be a new dimension in U.S.-China relations. But it's a multi-faceted relationship. We are cooperative, we're competitive, we're antagonistic on a variety of different issues. And the competition and antagonism on Taiwan I think will continue, because the Chinese will continue their military buildup. And so long as that continues, it seems to me, the United States side will have to take account of that."

Professor Nathan sees the war against terrorism presenting additional obstacles to good Sino-American relations over the long term because a prolonged U.S. campaign will mean an intensified American presence in central and south Asia.

If the events unfold in such a way that the U.S. establishes a strong permanent military presence in Pakistan and Afghanistan and in Central Asia, the Chinese are going to reasonably enough view that as an element of American encirclement of China.

Mr. Nathan says a new American presence on China's western border, in addition to the already strong U.S. military position in Japan and South Korea and the longstanding U.S. relationship with Taiwan, will present a security concern to Beijing and a new source of tension to the bilateral relationship.