One of Iran's highest-ranking Moslem clergymen yesterday sharply criticized legislators whose boycott prevented the parliament from considering the issue of the American hostages, and Tehran radio, in an apparent change of direction, said their release would be "a blow to the world's oppressors."

The developments came on a day of mixed signals -- but no direct action -- on the fate of the 52 Americans who, on Monday, will have been in Iranian captivity for a full year.

Ayatollah Hossein Ali Montazeri, generally considered a hard-liner on the hostage issue, was quoted by Iranian state television as saying that the boycott Thursday of a parliamentary session that was expected to vote on release of the Americans "is unacceptable to the Moslem and revolutionary people in Iran," Reuter reported from Tehran.

The Tehran radio statement, broadcast only on the Arabic international service and not domestically, said Iran had already forced the United States to make concessions for the hostages' release and that the "year of punishment' they have endured would be "a good lesson for tyrants."

But Iranian Prime Minister Mohammed Ali Rajai devoted much of his address at a Tehran University prayer meeting to a harsh condemnation of the United States and a warning that Iran should "not show the least inclination toward the oppressor in order to obtain what we do not have."

In an unexplained series of moves, Iranian President Abol Hassan Bani-Sadr scheduled and then called off a news conference today. There was no indication whether the conference was to have dealt with the hostages.

Meanwhile, a Swedish charter airline confirmed reports that it had been asked whether it could have a plane ready a short notice to take the hostages out of Iran. But Georg Olsson, chairman of Scanair, said that the request was made a week ago by "an unnamed party" and that there had been no contact since.

Barring further changes in a situation that has no recognized timetable. Iran's parliament remains scheduled to reconvene at 8 a.m. in Tehran Sunday (11:30 p.m. today EST). At that time, another effort is to be made to hold a public discussion of proposed conditions for the hostages' release and to vote on the proposal.

On Thursday, enough radical members of the parliament who oppose releasing the hostages boycotted the session to prevent formation of a quorum needed to convene.

Montazeri's criticism yesterday of the boycotting legislators and a vehement condemnation of them Thursday by Ayatollah Sadegh Khalkhali, one of the most anti-American of Iran's Islamic clergymen, showed clearly that the country's mainline religious leadership wants to come to a decision on the hostage issue. Montazeri has frequently been mentioned as a possible successor to Iran's supreme religious figure, Ayatollah Ruhollah Khomeini.

In a telegram to the speaker of the Majlis, or parliament, Montazeri, according to Reuter, said that "failure to attend the Majlis and thus make a quorum is unacceptable to Moslem and revolutionary people in Iran. We are expecting that these honorable gentlemen pay more attention to this important question."

The broadcast by Tehran radio, which in the past has been associated more with the hard-line position of the militants holding the hostages than with the government, said that "the Iranian people led by the great Imam Khomeini have drafted a just method for the release of the hostages."

Islam has already "emerged victorious from its struggle with the United States over the spy hostage issue," the radio said, and has "forced the United States to make concessions.

"The seizure of the spy hostages was a bold human act by the heroic Iranian people," the radio said. "The detention of these spies for one year is an unforgettable lesson for those who let themselves be seduced into working in this ill-fated field. It is also a good lesson to tyrants who rely on such unethical methods to carry out their oppression.

"They have spent a year of punishment," the radio said, and "from Iran's viewpoint their release is the way to expose the long criminal history of the United States."

The Tehran radio commentary was followed immediately by another, also broadcast in Arabic, cautioning Iran against giving in to what the commentator saw as a U.S. move to resume normal diplomatic relations once the hostages are freed.

"If the United States is able to resume relations by means of the hostages' release, it will then be the winner despite the concessions it is offering," the radio said, because it would continue to oppose Islam. Resumption of relations, it said, "would be the beginning of a new conspiracy against the safety and sovereignty of the Islamic government."

Rajai's speech, possibly tailored to his usually hard-line young audience at the Friday prayer service at Tehran University, referred repeatedly to the American hostages as "spies" and said that as a result of the embassy seizure "the world realized that it was a nest of spies, not an embassy."

He again accused "this arch-Satan," the United States, of formenting the war between Iraq and Iran and warned against letting the issue of the hostages be decided on the basis of money or military spare parts from the United States.

"We are not prepared, not even for a single moment, to become the servants of the United States in order to obtain the spare parts," he said to cheers of "God is great!"

He commended the students and young people who overthrew the late shah for their rapid maturing during the revolution.

When the shah "saw that those young men who in the past used to hang around the alleyways and whistle at girls now come forward to work sincerely to distribute kerosene, tea and other necessities," Rajai said, "he deemed the revolution victorious and himself defeated."

Islamic student groups yesterday called demonstrations across the country for Nov. 4 to mark the first anniversary of the seizure of the U.S. embassy as well as the anniversary of Khomeini's exile to Turkey in 1963 and an attack two years ago by th shah's troops that killed several university students.