Secretary General Kurt Waldheim announced today that he will go to Tehran Monday with the approval of Iranian authorities to discuss the situation of the Americans being held hostage there.

[Iran's Revolutionary Council announced that it accepts -- grudgingly -- the attempt by Waldheim to negotiate the release of the hostages, but Islamic leader Ayatollah Ruhollah Khomeini said he had no plans to meet with Waldheim and militants occupying the U.S. Embassy in Tehran rejected his mission before it was officially announced. Details on Page A7.]

Waldheim's surprise announcement came as the United States introduced into the Security Council a proposed resolution calling for the 15-nation council to impose economic sanctions against Iran if Waldheim is unable to secure the captives' release by Jan. 7.

Although several council members left unclear in tonight's formal debate their reaction to the resolution, a senior U.S. official said the United States is confident the resolution will gain at least the nine votes necessary for adoption when it comes to a vote Monday.

The official, who declined to be identified, refused to predict the actual tally. However, the United States is known to believe that the resolution will be backed by 11 council members.

In addition to the United States, those countries expected to vote in favor are Britain, France, China, Norway, Portugal, Bolivia, Jamaica, Nigeria, Zambia and Gabon.

Expected to abstain or vote against are the Soviet Union, its communist bloc ally Czechoslovakia, and Kuwait and Bangladesh, both Islamic countries located in the same southwest Asia region as Iran. However, the Soviet Union, a permanent council member with the power to veto the resolution, is expected refrain from blocking adoption of the resolution by abstaining in the vote.

In order to line up the necessary votes -- particularly those of China and the three African members -- the United States was forced to accept a two-stage approach. The practical effect of the approach will be to postpone until after Waldheim's trip to Tehran the actual defining and imposition of any economic measures the council may impose against Iran.

Instead of spelling out what the specific sanctions should be, the draft resolution calls on Waldheim to make another attempt at securing the hostages' freedom and to report the results of his mission to the council by Jan. 7.

Then, the resolution states, "in the event of noncompliance," by Iran the council should "adopt effective measures under articles 39 and 41 of the Charter of the United Nations." These articles authorize "complete or partial interruption" by U.N. members of economic and communications links with any country whose actions are deemed by the Security Council to represent a threat to world peace.

U.S. officials contend that this language, if adopted, would commit the council to impose some form of sanctions should Waldheim's mission fail. But, that contention is disputed by several U.N. sources who note that the council's membership will change on Tuesday when five of the 10 non-permanent members complete their term's and are replaced on the council by other countries.

As a result, these sources say, the United States will then be back in the position of having to start a new lobbying campaign with the new council lineup to spell out what sanctions should be applied and when.

However, the senior U.S. official denied that the U.S. two-stage approach represented a retreat from President Carter's pledge to press forward quickly with his campaign for U.N. sanctions.

The official conceded that some of the council's Third World members were reluctant to vote for immediate imposition of sanctions without first giving Waldheim another chance to get on the record that he had tried to mediate the conflict between the United States and Iran's revolutionary leaders.

In addition, the official said, the United States concluded, during the consultations leading up to the council debate, that negotiating agreement on what the sanctions should be would have been so time-consuming that it would have prevented action before the change in council membership.

As a result, the official asserted, the United States opted for the two-stage vote from the present council and to accomodate those members who wanted what he termed "a final warning shot" delivered to Iran by the Waldheim mission.

In the meantime, the official concluded, the United States is in close contact with those countries continuing on the council and those who are about to become members in an effort to define what sanctions should be applied. That work is continuing, the official said, and in the event that Waldheim's mission fails to produce results, the council should be able to make a quick decision on spelling out the measures it will seek to apply against Iran.

The official refused to say what form these measures might finally take except that they would exclude food and medicine shipments to Iran on humanitarian grounds.