President Abol Hassan Bani-Sadr asserted Wednesday that he had received a message from President Carter "accepting" Iran's demand to refrain from public statements that could complicate efforts by Tehran authorities to gain custody over the American hostages held at the U.S. Embassy.

"We asked for Carter to say he would not say anything and he has sent a note saying he accepts that," said Bani-Sadr, speaking to reporters after his return from a brief visit to northern Iran.

The statement, which did not contain any references to Bani-Sadr's strident demand Tuesday that the American president make a formal public pledge to eschew either criticism or economic and political sanctions, appeared to leave the door open for movement on the transfer of the estimated 50 Americans held hostage here since Nov. 4.

But informed sources reported that Bani-Sadr was still undecided on whether to go ahead with the transfer.

In Washington, U.S. officials reacted calmly to Bani-Sadr's disclosure and characterization of the note. The U.S. sources said it was a government-to-government message that did nothing more than note that Washington was aware of what Bani-Sadr had said Tuesday. The officials reiterated that Carter has given no pledge to remain silent.

Informed sources here provided a separate but nearly identical description of the message, which noted that the Iranian government has said the new parliament will decide the hostage's eventual fate. The U.S. acknowledgment of the parliament's role was part of Bani-Sadr's conditions for transferring the hostages to the authority of the 13-man ruling Revolutionary Council.

The new message apparently fell well short of satisfying Bani-Sadr's call for Carter to publicly promise not to make any "propaganda, claims, speeches or provocations" about the hostages until the parliament can assemble to decide the issue, probably in late May or early June.

Rather than proclaiming the right to keep demanding the hostages' release, the message is reported to recall that the United States government's goal is to obtain their freedom as soon as possible. That formulation would fall short of Bani-Sadr's more stringent earlier demands to stop all propaganda efforts on the hostages' behalf.

The new message apparently dropped any hint of applying tough economic sanctions against Iran. Some sources, however, suggested that Easter Sunday constituted a new deadline for the transfer if such punitive measures were to be avoided.

Bani-Sadr was depicted as profoundly uneasy about the transfer, especially in light of Ayatollah Ruhollah Khomeini's own pronounced preference for allowing the new parliament to decide the hostages' fate.

No new decision was expected before Thursday evening, when the Revolutionary Council was scheduled to meet after a two-day, mid-week holiday.

There were reports that the government was considering having leading Moslem clerics visit the embassy to report on the hostages' conditions of detention. The last such visit -- by Ayatollah Ezzattollah Sahabi in early March -- confirmed earlier rumors of considerable mental strain, but no serious physical illnesses among the hostages.

Informed sources said that despite weeks of discussion, Bani-Sadr was still undecided about how to proceed with the practical physical problems involved in any transfer at the embassy.

Although the United States has rejected allowing the student captors to remain alongside the hostages in any transfer, Bani-Sadr was still said to be toying with such a solution.

Some Iranian insiders have argued that the students were capable of protecting the hostages, in contrast with the police. Revolutionary Guards or armed forces, whose loyalties are in some doubt.

The president was also reported hesitating whether to leave the students inside the embassy and remove the hostages, evacuate the students but leave the hostages, or remove both groups.

Reached by telephone from London, a spokesman for the militants told United Press International, "If the Revolutionary Council asks us to turn them [the hostages] over, we will not do anything opposed to them. The United States would first have to meet the terms," he added.

["We are not trying to take power from the Revolutionary Council, so whatever the Revolutionary Council says will be fine with us," the spokesman told the news agency.]

[The Associated Press, however, quoted a militant spokesman as denying that the students will turn the hostages over to the government. "We haven't said anything about this subject yet," he told the AP by telephone.]