AMERICA'S top China experts have issued a report urging the Clinton administration to strive for a normal relationship with Beijing through a policy of ''vigorous, intelligent engagement''. The report warns that a deterioration in United States-China relations would dangerously destabilise Hongkong and prod Beijing into adopting a more hostile military posture in Asia and beyond. It further warns that any punitive US action to reduce trade with China would similarly reduce Beijing's incentives for restraint in dealing with Hongkong. It said America's ''overriding interest'' concerning Hongkong's transfer to Chinese rule was that the change-over should serve the interests of Beijing and Hongkong people as well as US investments in the territory. The report said the Hongkong transfer posed a policy dilemma for Washington which faced the problem of having to protect its interests and values without appearing to be meddling in the internal affairs of China or Britain. In discussing Washington's policy towards Hongkong the report said: ''It is hard to envision any scenario under which Americans would, in fact, expend blood or treasure in the defence of Hongkong, except to rescue Americans in the event of a total breakdown of law and order.'' The report is compiled jointly by the Atlantic Council and the National Committee on US-China Relations. Entitled United States and China Relations at a Crossroads , the report warned that a passive policy towards the People's Republic of China would be an ''unfortunate mistake''. It said only an active policy of engagement would enable the US to gain Beijing's co-operation in achieving common goals and resolving differences. Co-chairman of the experts' panel Mr John Whitehead, a former deputy secretary of state, said quiet high-level diplomacy was the best way to bring about better Sino-US ties. The other co-chairman, Mr Barber Conable who is a former World bank chairman, said: ''We feel the Chinese leadership is much more likely to respond to quiet diplomacy.'' In calling for a ''vigorous human rights dialogue'' with China the report said the US must know precisely what progress it wants to see in this area and make clear to Beijing human rights is not an ''internal matter''. In an apparent reference to the ongoing efforts by Congress to impose human rights and other conditions to the renewal of China's Most Favoured Nation trading status, the report warned that the US should avoid letting one issue dominate bilateral relations. It said debate on the issue should be put off for a year while the new administration assesses the progress of a new dialogue with China on human rights. The report recommends resuming high-level military exchanges and dialogue on other global issues andrestoring loan guarantees to US businesses involved in China trade.