The Iranian parliament today began a session in which conditions for the hostages' release were scheduled to be announced, but then voted to hold a debate on the terms in secret later in the day.

The decision was reached about 1 1/2 hours after the parliament began its session, which soon became bogged down in dissension over whether to hear a report on conditions for the hostages' release or postpone deliberations on the subject altogether. The session was being carried by Iran's state-run radio in an unusual live broadcast that sources in Tehran said was intended to allay public concerns that a secret deal with the United States might be reached.

Several deputies then argued that more candid discussions could take place in private, and some insisted that the debate be deferred because of a fierce rocket attack on the southwestern Iranian city of Dezful last night by Iraqi forces in the continuing Iranian-Iraqi war.

Reuter news agency reported from Tehran that the proposal for a closed-door session was supported by one of the members of a seven-member commission set up to recommend terms for the hostages' release. He said, without elaborating, that the commission wanted to air some points that could not immediately be made public. The parliament then decided to hold the private session as another commission member was about to deliver its report, Reuter said.

In opening the session, parliamentary speaker Hojatoleslam Ali Akbar Hashemi Rafsanjani said that a report by the special commission would be the sixth of eight items on the agenda, Reuter reported.

Some of the preceding items were procedural formalities, but they included a discussion of underground water supplies.

The official Iranian radio began broadcasting the session live when it started at 8 a.m. Tehran time, about a half hour late.

Iranian sources said the parliament wanted to avoid giving the impression that it is softening its terms for freeing the captives, especially in the midst of a costly war with Iraq. Another factor that could affect the proceedings was that today is the late shah's birthday. A knowledgeable diplomatic source said this coincidence would not be lost on the parliament and would tend to make any dramatic breakthrough today unlikely.

Earlier, several Iranian officials involved in parliamentary deliberations on the hostages said that the Americans might be released in stages rather than together, according to news service reports from Tehran.

However, the statements from Iranian authorities yesterday continued to reflect conflicting views about what should be done with the hostages a day before a special seven-member commission was scheduled to report to the parliament on conditions for the captives' release. There were signs that militant Moslem fundamentalists, who back the hostages' captors, were still pushing for tough conditions, if not scuttling of the prospective release.

There was no frim statement from any Iranian official on when such a release might occur.

A spokesman for Prime Minister Mohammed Ali Rajai denied an American news report that the hostages could be freed as early as Sunday.

But the French news agency Agence France-Presse reported that five members of parliament, who have read the recommendations of the commission, said that the hostages might be released in stages. The five also told AFP that the commission has recommended the same four conditions proposed by Ayatollah Ruhollah Khomeini on Sept. 12. These are the release of frozen Iranian assets, cancellation of all claims against Iran, return of the late shah's property and a promise not to interfere in Iranian affairs.

The prospect of a piecemeal release was given further credence by former foreign minister Sadegh Ghotbzadeh, who played a major role in past efforts to negotiate a settlement of the hostage issue. He told a Japanese television reporter in Tehran yesterday that release in stages was possible. Ghotbzadeh also said that he believes there is no longer a major gap between the United States and Iran on conditions for the hostages' release and that Washington has already satisfied any demand for an apology for its past support of the shah.

In another statement on the subject, Ayatollah Moussavi Khoeini, a member of the parliamentary commission on the hostages and a mentor of the Moslem student captors, said that the Americans would be freed when the United States fulfills all Iranian conditions, but that some could be released sooner if Washington satisfies some terms.

"There is a possibility we could show good will if the U.S. shows the same," Khoeini told AFP in an interview.