President Carter has not signed off on Presidential Review Memorandum 24, the National Security Council document that sets forth the basic options of China policy. He is awaiting the outcome of the visit to Peking this week by Secretary of State Cyrus Vance, for the China trip is a true test, with unambiguous marks of success and failure.

At stake is the status of Taiwan, the offshore island claimed by the People's Republic, but now held by the Chinese Nationalists, who enjoy both diplomatic ties and a defense treaty with the U.S. Success lies in moving relatons between Washington and Peking off the dime without making major concessions on the present status of Taiwan. Failure occurs if Taiwan is pushed to the top of the Sino-American agenda.

Reasons abound for not putting into question American diplomatic and defense support for Taiwan. Despite solid claims for the island, Peking does not have - and is not developing - the military equipment required for a successful invasion. Far from helping Peking, severance of American diplomaticand defense ties would only expose the inability of the People's Republic to make good its claim.

If the United States did sever ties, moreover, the regime on Taiwan might easily take steps - such as going nuclear or declaring independence or striking a deal with Russia - that, by hardening its existence, would edge toward the nightmare of two Chinas. Any move to change American support for Taiwan, furthermore, would run into heavy flak in the U.S. Senate, just as a bunch of other issues - notably the Panama Canal, but also arms control - draw on all of the political capital the Carter administration can muster on foreign policy.

Set against the debits connected with a (largely symbolic) change in the status of Taiwan are the assets that flow to Peking from ties with the United States. This country is the only available counterweight against the great power to the north that is still China's No. 1 enemy: the Soviet Union.

These consideratins were obviously dominant back in 1972. To be sure, major changes have taken place in the interim. Among other things, new regimes have come to power in Peking and in Washington. Most leading China experts believe along with Sen. Edward Kennedy that China will move forward in cooperation with the United States only if this country speedily ends its diplomatic ties with Taiwan and subsitutes a new declaration of support for the existing defense treaty.

But personally I wonder. Over the past two years, Chinese leaders have made comments on Taiwan covering a wide range of views from "settlement by negotiation" to "liberation by force." But those views were expressed during a king of interregnum following the deaths of Premier Chou En-lai and Chairman Mao Tse-tung.

Now the interregnum is over, and the successors are in place. They have been freshly mandated by the 11th Party Congress. So they may have the political strength to be patient on the shadow of Taiwan if they can get the substance of American support around the globe.

This "if," unfortunately, is a big one. Vance visits Peking only after trips almost everywhere else in the world. Administration emphasis on human rights and support of blacks in Africa - as well as its seesaw on arms control with Russia - have give the Chinese reason to wonder whether President Carter is not chasing after a pack of wild hares.

In Peking Vance will have to explain himself and the President. He will have to provide the Chinese with an underlying rationale for American policy toward Russia, Europe, the Mideast and the Third World. He will have to show that American has a place for China as an actor on the world stage.

If the Secretary can do that, then Washington may be able to scrape by with Peking. There will be at least a chance of expanding trade and cultural relations over a period of time, while putting off for four or five years normalization of diplomatic relations with Peking and a change in the status of Taiwan.

If the secretary cannot do that, then the severing of old ties with Taiwan may indeed be necessary. But it should be undertaken only as a last resort, only if it becomes clear the otherwise the U.S. will lose its position as master of the three-way game that still obtains between Washington, Peking and Moscow.