For a long list of reasons - from Tibet to Taiwan to trade - this promises to be a testy year for Sino-US relations. It is clear one topic of dispute will be the recurring one of American exports of advanced technology to Beijing. A congressional study just last week called for tighter controls, including on supercomputers. Those who favour new restrictions argue that the United States should not sell China equipment of potential military value while their long-term security relations remain so ill-defined and while human rights disputes persist. It does not help that some Americans who want tougher rules also hope to turn China policy into a political weapon for beating President Bill Clinton, whom they dislike. Among other things, the congressional study, drafted by a special House committee on high-technology trade with China, calls for restrictions on supercomputer sales, tighter security at US nuclear weapons laboratories so Chinese spies cannot steal secrets and new licensing procedures for exporting technology with military applications, such as encryption equipment. But little of this is new. Quarrels about hi-tech exports to present or potential adversaries are an old issue in American politics. And if the US Government has a special legacy of trouble regarding China, it could, at least in part, be one of its own making. Thanks to some recently declassified American documents, details of a prior computer sale to Beijing are now on public record. They show a US president and secretary of state colluding eagerly with Chinese leaders on a deal which might have violated broader export restrictions. Their purposes: to do something positive for a Sino-US relationship which was having problems because of the Taiwan issue and to prevent 'nihilistic' American journalists reporting ties were cooling, which they were. The time was a December 1975 summit in Beijing; the main actors were president Gerald Ford, secretary of state Henry Kissinger and vice-premier Deng Xiaoping. The Americans wanted to issue a joint communique which said relations were good and getting better. But the Chinese refused. If the US would not sever defence and other links to Taiwan and transfer official relations to Beijing, they would not pretend things were fine. So Mr Ford and Dr Kissinger decided to supply a couple of high-speed computers, which the Chinese wanted, to let the summit close on a positive, if secret, note. These had potential military uses and could not then be sold to the Soviet Union for security reasons, but the Americans were determined to go ahead. They hoped to make official toasts at the final banquet more upbeat. 'Our problem,' said Dr Kissinger as [the transcript shows] Mr Deng spat into his spittoon, 'is we have refused certain computers to the Soviet Union.' So if Chinese trade officials sought them through normal channels, he warned, the White House would have to say no. 'However,' he continued, 'there is a better way: tell us privately what you need and we'll find a model with enough technical differences to slip past the law, but which will do the job.' President Ford added: 'I would like you to know, Mr Vice-Premier, that we are very anxious to be helpful.' 'Fine,' responded Deng, but he clearly was not impressed. 'We think the solving of specific issues like this, or their all remaining unsolved, will not be of great effect to our general relations.' At which point the transcript notes: 'The Chinese all laugh'. The deal went through. Two Control Data Corp (CDC) high-speed computers were sold later, ostensibly for the oil industry, but also suitable for missile testing and nuclear weapons design. In fact, the Soviets also obtained CDC computers but only because they let their use be monitored; the Chinese were not asked to do the same. Today's problem is similar. Critics claim Mr Clinton, like Mr Ford, is too ready to ship sensitive technology, partly to offset other quarrels and keep Sino-US ties intact. For the White House, this continuing dispute may reflect that Biblical warning about reaping what you sow.