If there was ever a time for Chinese and American leaders to give serious thought to the future of their relationship, that time is now. A seemingly random series of past and pending events is pushing them into increasingly unfriendly exchanges. Letting that dangerous trend continue directly contradicts their basic interests and those of the entire region. The immediate issue is the fate of the US surveillance plane that made an emergency landing at a Hainan military base after a midair collision with a Chinese fighter; the fighter crashed and its pilot was presumably killed. Beijing says the whole thing was the Americans' fault, that the lumbering propeller plane swerved sharply and hit one of the two fighters that were tailing it. Washington suggests that Chinese jets having been flying perilously close to their patrol craft for months and that the fighter was probably at fault. This incident recalls similar Cold War cases involving US spy planes and ships. And it comes just as other items threaten to sour the Sino-American relationship, well before the new George W. Bush administration has sorted out its foreign policy in general and China policy in particular. The augury is not favourable. In addition to the plane issue, other matters are influencing US-China ties in an undesirable way. Foremost among them is the pending US decision about selling new arms to Taiwan. Some island authorities want a new class of destroyer with modern Aegis radar systems, upgraded versions of Patriot anti-missile missiles and submarines. Many conservative American politicians agree, both because they distrust mainland intentions towards their Taiwanese friends and perhaps because such sales would bring fat contracts to their home districts. But Beijing, which realises (reluctantly) that some sales are unavoidable, insists providing those three weapons would cross into politically unacceptable territory. Thus some members of the Bush team must put aside their hawkish instincts and consider carefully just what Taiwan truly needs and why. It also means Beijing must accept, in reality if not in law, that military actions around the Taiwan Strait - where its missile forces are growing - directly affect what weapons Taipei does receive. Restraint fuels restraint, while a lack of it does the opposite. Another complication is the new practice of Beijing's national security officials questioning or even arresting ethnic Chinese scholars who return for research or holidays. At least three are in custody now, two for unexplained reasons, while a reported five more US-based scholars have been interrogated and released in recent weeks. This signals to Chinese academics that studying or living abroad (especially in America) is risky, and that re-visiting China is particularly dangerous. Yet this contradicts the official Chinese policy of trying to woo back scholars who have gained foreign degrees. Beijing must think through just what message it means to send and make sure the police are not exceeding their brief. And the US must be scrupulous about making sure that it avoids even the appearance of using these vulnerable academics for intelligence purposes. China's basic policy is to pursue economic development. America's basic interest is to preserve regional stability, while promoting trade and investment. These are common and fundamental goals. That is why it is essential that top leaders on both sides step back and analyse anew just where they want their mutual relationship to go. It could be disastrous for both, and for all of East Asia, if new tensions block exchanges which serve both sides so well. And it would be especially tragic if this happened because lesser issues got out of control and the relationship deteriorated more by accident than design.