Sino-American relations are in the doldrums, and only a high-level visit such as one by United States Secretary of State George Shultz is likely to put them back on course.
The tone of Sino-American exchanges has become sharper since the joint communique of Aug. 17, according to a Chinese observer. He was referring to such things as American restrictions on Chinese textile imports, and on transfer of high technology as well as Chinese irritation over the case of Hu Na, a tennis champion who has sought political asylum in the United States.
None of these problems are important enough to shake the foundation of Sino-American relations. Despite China's less confrontational attitude toward the Soviet Union the premise of Sino-American strategic cooperation - defense against the threat of Soviet expansionism - still stands. Chinese officials have been quite categorical on this point.
They are equally categorical that the Taiwan problem is the major obstacle in the path of improving Sino-American relations. The seriousness of the Reagan administration's efforts to settle the vexed question of American arms sales to Taiwan - efforts that led to the joint communique of Aug. 17 - is well recognized. But they are concerned about the efforts of Mr. Reagan's right-wing supporters to upgrade American relations with Taiwan.
They are disturbed by every little sign of official American contacts with the Taiwan government such as National Security Adviser William Clark's presence at Taiwan's National Day celebrations in Washington Oct. 10. Chinese sources, both official and unofficial, agree that mainland China and Taiwan are not likely to be reunited for many years to come and that peaceful reunification can come only as the mainland's economic level and living standards begin to approach those of Taiwan.
But no Chinese, officially or otherwise, can accept that Taiwan and the mainland shall remain forever separate. It was only the American admission that Taiwan was a part of China that made possible the normalization of relations between Washington and Peking, and it was only the Reagan administration's acceptance of this position that keeps Sino-American relations viable.
What the United States is committed to is that a change in Taiwan's status should come about only through peaceful means. Peking has never officially accepted this position, but the tortuous and eventually successful course of Sino-American negotiations over arms sales to Taiwan shows that Peking is willing to accommodate the United States to some extent, considering, as the authoritative magazine Liaowang put it recently, that Taiwan is ''a problem left over from history.''
Sino-American relations need careful tending precisely because the Taiwan problem, by its very nature, is not likely to see a clean or clearcut solution for many years to come. That is why high-level visits are important. That is why visits such as those of Vice-President George Bush and of Senate majority leader Howard Baker were essential to the final compromise worked out in the communique of Aug. 17. Since his nomination as secretary of state, Mr. Shultz has been preoccupied with the war in Lebanon and with the pipeline dispute between the United States and its European allies.
Meanwhile, the Soviet Union has been playing its own ''China card'' to the hilt. Peking has responded to the extent of holding ''consultations'' with a Soviet emissary in Peking. The next round is to take place in Moscow - probably, Chinese sources say, not before next year.
China's rhetoric toward the superpowers has changed in recent months, and it appears as though Peking is crying a plague on both Washington and Moscow. But Chinese sources point out that their appraisal of Soviet expansionism - ''hegemonism'' as they put it - as the main threat to world peace has not changed.
They may attack the United States specifically over its support for Israel or for South Africa. But this does not mean their view of the need for continuing strategic cooperation between the United States and China against the Soviet threat has changed. One source even said that Chinese support for third-world countries, to the extent that it keeps these countries from turning to the Soviet Union, is one aspect of Peking's strategic cooperation with the United States.
So, looking beyond immediate frustrations, there is a continuing community of strategic interests between China and the United States. As soon as Mr. Shultz is able to draw a breath and to fit the China relationship into the United States global strategic considerations, a visit to Peking should prove useful in clearing the air and in sorting out fundamentals from peripherals.