A four-step scenario for the immediate release of the American hostages in Iran appeared highly uncertain of accomplishment last night as both Iran and the United States headed into several days of crucial decision-making.

Senior administration officials, including White House counsel Lloyd N. Cutler, denied rumors and reports that a deal has been worked out between the two countries for the hostages' release by Tuesday, Election Day in this country and the one-year anniversary of the seizure of the U.S. Embassy compound and diplomatic personnel in Tehran.

Specifically, Cutler described as "totally false" assertions by columnist Rowland Evans and Robert Novak in a special report to newspaper clients that the hostage-release deal was "sealed in a handshake" between Cutler and Iranian emissaries in Geneva a little more than two weeks ago.

Cutler said he has not been out of the country since May, when he went to Paris on a trip involving the boycott of the Moscow Olympics. He said he has not been involved in negotiations with any Iranians or representatives of Iran, though he is involved in Washington discussions of the U.S. position on meeting the likely Iranian demands.

Cutler and other senior U.S. officials continued to take a posture of watching and waiting in yet another day of suspense as the Iranian power structure struggled with the hostage issue in Tehran. These sources said they have no advance assurance about the result of an expected Sunday session of the Iranian Majlis, or parliament, that has been called to debate the terms for the hostages' release.

One senior official estimated the chances at about 50-50 that the Majlis will be able to agree tomorrow on official Iranian terms for release of the Americans, but another official who is an expert on Iran put the chances at no better than 10 to 20 percent that the parliament will be able to reach a decision tomorrow.

If and when the Iranians agree on their terms for release of the hostages, this is expected to be only the first of four steps in the process of bringing the Americans home, according to administration sources. The other three steps are: U.S. agreement to meet the Iranian terms, Iranian agreement that the terms have been satisfactorily met, and, finally, the movement of the Americans out of Iran on a flight to a German medical way station en route home.

That all this can be accomplished between tomorrow morning, when the Iranian parliament is to meet again, and the U.S. balloting on Tuesday is considered highly uncertain by those at the top of the U.S. government.

The American realities as well as those in Iran are more of a question mark than is indicated in the speculation that has been sweeping Washington and the nation. Coming down to the wire in a hotly contested race for reelection, President Carter would be in a poor position on election eve to agree to any Iranian terms that seemed to flow from his political needs of the moment.

Some in the Carter camp expressed suspicion yesterday that the political opposition -- the Ronald Reagan camp -- is the source of at lest a portion of the rumors and assertions that a deal is all set. By raising public expectations, the reports tend to damage Carter in the event the hostage release is not accomplished before the election, and to rob him of political benefits if the release does take place.

In order to protect the president against charges that he caved in to Iranian demands in disregard of U.S. national interests, the White House is planning to consult congressional leaders about the Iranian terms before Carter replies -- if and when he has something to reply to. In any case, officials said, it would be impossible in these circumstances for Carter to agree to any terms that are not widely seen as clearly in the U.S. interest. a

The president and lesser officials have made the point in recent days that the U.S. positions on Iran's likely demands have not changed since early in the year, when the United States gave detailed information to Iran as part of a negotiated deal for the hostages' release. The deal fell apart at the last minute because of opposition from hard-line clerical elements in the Iranian leadership.

Nevertheless, there is no doubt that a large number of further refinements and practical details have been under study and discussion in policy-making circles here in recent days. These involve such matters as the blocked Iranian assets in the United States, which may be turned over to a third party as an interim step in their release to Iran under some of the plans under discussion.

The most highly controversial and internationally difficult matter is the supply to Iran of U.S. spare parts and other military equipment bought and paid for by Iran before the taking of the hostages, but withheld from shipment due to a presidential embargo. Despite reports to the contrary, a senior official said the United States has no intention of supplying missile parts or lethal weapons to Iran as part of the hostage arrangement in view of the Iran-Iraq war.

If the Iranian parliament does reach its decision tomorrow, it is still uncertain how the United States will make its response. Consideration has been given to a presidential address or statement late tomorrow or Monday. Another possible forum is an appearance by Secretary of State Edmund S. Muskie on ABC's "Issues and Answers" tomorrow at noon.