The future of Sino-American relations may depend on how China reacts to the forthcoming United States arms sale to Taiwan.
Peking could recall its ambassador in Washington for ''consultations.'' It could decide formally to downgrade diplomatic relations with the US to charge d'affaires level. Or it could remain silent.
The Reagan administration, according to Western diplomats here and sources in Washington, is leaning over backward to present the arms sales in as palatable a light as possible.
Secretary of State Alexander M. Haig Jr. called in the Chinese ambassador to the US Chai Zemin April 5 in a bid to win Peking's acceptance of an American proposal on arms sales to Taiwan.
The sales are described as $60 million worth of spare parts rather than as arms properly speaking, and are said to include items such as aircraft parts and caterpillar treads for tanks. Washington asserts they are the minimum Taiwan requires to maintain a viable defense.
China's senior leader Deng Xiaoping recently said that ''China was recognized as a sovereign state and there is only one China. The sale of arms to a part of China is a contradiction. There is no room for maneuver, no give on this issue.''
Mr. Deng told visiting former British Prime Minister Edward Heath that the US should stop trying to run Taiwan as an American aircraft carrier.
Yet the talks begun between Washington and Peking last November continue. However, the Reagan administration's decision to go ahead with the arms sales could signal the breakup of the talks.
Diplomatic sources here believe Peking might choose to continue the talks in the hope of bridging the gap between Chinese demands for stopping arms sales and the Reagan administration's legal responsibility to defend Taiwan.
Mr. Reagan came to office pledging to upgrade Taiwan's relations with the US and to provide Taiwan with more and better weapons. So far he has not ''officialized'' relations with Taiwan. But he has carried on arrangements previously made by the Carter administration for unofficial trade and cultural relations.
On weapons sales, he made a landmark decision early this year that Taiwan did not need advanced F-16 fighter bombers. But Taiwan will get a continuation of present joint production arrangements in Taiwan for the F-5E fighter.
Furthermore, the spare parts sale to be announced soon is the first major arms sale contract the Reagan administration has provided Taiwan since it came to office 14 months ago.
The announcement will take the form of a notification to Congress. The administration is legally required to inform Congress of all arms sales contracts exceeding $50 million. The notification is expected before the Easter recess and, if no objection is made by Congress within 30 days, the sale will proceed.
The Carter administration, which normalized diplomatic relations with Peking and downgraded Taiwan's diplomatic status, had much more cordial relations with Peking than does this administration. Yet the Carter administration sold vast quantities of arms to Taiwan.
Mr. Reagan has measurably decreased the flow of American arms to Taiwan. Deliveries under contracts made before he took office continue.
But if new contracts are made as sparingly as they have been so far, there is little likelihood that they will approach the $800 million and more that the Carter administration supplied Taiwan.
Peking is not insisting that Washington stop all arms sales to Taiwan immediately. What it wants is an American commitment that arms sales will decrease and eventually cease.
So far Washington has not been able to give this commitment because it would infringe on the Taiwan Relations Act. Peking has consistently opposed this act. But in Congress' present mood, it would be exceedingly difficult, if not impossible to revise.