The election of a new U.N. secretary general remained stalemated today despite incumbent Kurt Waldheim's withdrawal from the balloting, as everyone waited for a decision from the other current candidate, Foreign Minister Salim A. Salim of Tanzania, on whether he will also step aside.

The most nervous of the waiters were the other potential contenders for the $158,000-a-year job, none of whom is likely to enter the ring until Salim -- the official candidate of the Organization of African Unity and the nonaligned nations -- has withdrawn.

Salim seems in no hurry to respond to the withdrawal request from Security Council President Olara Otunnu of Uganda. He put the question to a meeting of OAU ambassadors last night. They declared Salim still to be their candidate but in fact are asking their governments what step to take next.

Some Africans say Salim may want to test his candidacy one last time in the council, where the American veto has blocked him on 16 previous ballots during the past five weeks. But no one expects a change in the American stand, because the United States has openly encouraged the emergence of new candidates.

It may be late next week before Salim finally bows out and the new contenders assemble, but time is running short because the General Assembly, which must approve the council's choice, is scheduled to adjourn on Dec. 15.

It is far from certain that the council will reach agreement on a replacement even by Dec. 31, when Waldheim's second five-year term expires.

The time factor has led many diplomats to believe that Waldheim's withdrawal from the balloting was tactical, and that he remains available to be drafted by consensus for an extension of his present term. But the secretary general issued a "categorical" statement today emphasizing that the sole purpose of his decision "was to facilitate the council's consideration of this difficult question."

The Chinese, who have blocked Waldheim with their veto on each previous ballot, reaffirmed to reporters today that they remain adamantly opposed to extending Waldheim's stay in office. The Soviet Union has hinted that so long as there is a chance for Waldheim, they may veto everyone else.

There are three men so far whose names have been widely mentioned as potentially acceptable to Moscow.

One is Mexican Foreign Minister Jorge Castaneda, who is viewed as unusually independent of American influence.

Another is Javier Perez de Cuellar of Peru, a diplomat and former U.N. under secretary who is described as "a Latin American Waldheim" -- a man of caution who would pose no threat to any big power.

The third is Prince Sadruddin Aga Khan, the former U.N. High Commissioner for Refugees, who sees himself as the most effective bridge between the Third World and the industrialized nations.