Faced with growing defiance by the militants holding the U.S. Embassy, Iran's ruling Revolutionary Council today put off a possible confrontation by giving them another 24 hours to decide whether to transfer their American hostages to government control.

The plan to turn over the estimated 50 American captives to the Revolutionary Council appeared further comprised as the idea's principal proponent, Foreign Minister Sadegh Ghotbzabeh, became increasingly isolated within the council.

After a three-hour evening council meeting, Ghotbzadeh told reporters that the militant captors 'have to decide within 24 hours one way or another" to transfer the hostages to council authority or allow a United Nations fact-finding commission to visit all the Americans.

Ghotbzadeh's statement appeared to fall well short of an ultimatum.He did not say what, if any, government action would be taken if the militants failed to comply with either demand.

Earlier today, the embassy militants had escalated their conditions for a transfer after reiterating their refusal to allow the commission to visit the embassy on the ground that such a move would be "deviationist and impossible."

In a tough late-afternoon statement to the official Pars news agency apparently designed to spur the Revolutionary Council into taking effective action against the militants, Ghotbzadeh said the new conditions showed that the captors "do not intend to hand over the hostages at all and do not intend that the international commission should meet them."

Piqued that the state-run television and radio networks communique offering to hand over the hostages to the Revolutionary Council between 10 a.m. and 5 p.m. today, the militants, in a second statement, said any handover would take place "at a new time to be announced later."

In a three-hour midday meeting with high-ranking Foreign Ministry officials, the captors said any transfer was conditional on receipt of written orders from the Revolutionary Council, eight hours advance warning about the transfer's timing and the captors' access to radio and television during that period.

In commenting on the militants' demands, Ghotbzadeh also said: "It is also certain that their objective in announcing the exact time of the transfer is that the 1,000 and 2,000 people who regularly gather [outside the embassy] -- and their nature is clear to everybody -- should prevent the hostages' transfer so that the students may announce that the nation has asked them to keep the hostages."

Informed sources said the Revolutionary Council members still hope the militant's will allow the five-man U.N. commission to visit the hostages.

In an evening television appearance that Ghotbzadeh claimed elicited a flood of favorable telephone calls, he attacked the militants for defying the Revolutionary Council, which he said was "legal and accepted" by Ayatollah Ruhollah Khomeini and followed his line.

"Any kind of opposition to the Revolutionary Council aims to disobey the imam's line," he said in paraphrasing the militants' own description of themselves as Khomeini's followers.

Although disappointed by succeeding unkept government promises that the visit to the hostages was imminent, the commission reportedly was willing to stay on despite its known desire to return to Geneva and write its report to U.N. Ssecretary General Kurt Waldheim.

In what was seen as an indication of the Revolutionary Council's own internal division, neither the captors' new conditions nor Ghotbzadeh's commentary was broadcast on either the evening radio or television news.

Instead, television showed a long two-day-old interview with the militants reiterating their now standard objections to the commission as "American-oriented."

That was followed by a long Ghotbzadeh soliloquy attacking the captors as an alternate power center illegally opposing the Revolutionary Council.

The only moderately hopeful developments of the day were imprecise suggestions emerging from the Revolutionary Council meeting that all its members may visit Khomeni Monday in hopes that he will decide what to do.

Yesterday, Khomeini's office issued a statement saying he had remained "silent" about transferring the hostages from the embassy. This fence-sitting position apparently reflects Khomeini's fear of alienating public opinion which still is said to favor the militants' hard-line approach to the hostages.

Behind the power struggle over the hostages are the stakes represented by the parliamentary elections, the first round of which are scheduled for March 24.

Outmaneuvered by Abol Hassan Bani-Sadr's landslide presidential victory in January, the right-wing clerical Islamic Republican Party has backed the captors now in apparent hopes of stalemating him on the hostage issue and thus preventing his candidates from achieving an equally impressive score in the parliamentary elections.

Influential Islamic Republican Party clergymen such as Ruhollah Moussavi Khamenehi, Hashemi Rafsanjani and Mohammed Beheshti are all on record as opposing the plans to transfer the hostages to government control, They have been joined by the left-wing islamic Mujaheddin, who have been much in evidence in the crowds outside the U.S. Embassy lately.

Earlier in the day, Ghotzbadeh, in an interview with four American correspondents, again expressed support for transferring the hostages to Revolutionary Council authority "because we don't want any of these chaotic situations ever to occur again."

He expressed doubt that the students would allow the commission to visit all the hostages, and said the Americans' transfer was "a foregone conclusion."

He lashed out against the militant student captors for "manipulating radio and television continuously yesterday" to give the impression that the "not more than 3,000" demonstrators supporting the militants were much more numerous.

Rather than talk about using force to remove the hostages from the captors' control, he indirectly threatened to call out "our people" who are willing to intervene if we ask them ." presumably by participating in counter-demonstrations against the militants' backers.

"That," he said, "was the greatest force we have and we could use it at any time we want."

Reacting to President Carter's willingness to express concern about past American interference in Iranian affairs, Ghotbzadeh for the first time admitted that all the errors in the present crisis have not been committed by Americans.

He said the present U.S.-Iranian crisis "unfortunately has been mostly the fault of American officials" who made "wild statements here and there -- and sometimes from here."

He again stressed the need for "step by step" consideration of each successive aspect of the crisis. He made clear that this meant concentrating on making the commission's visit here a success.