Iran's foreign minister today expressed doubts that any of the 50 American hostages here will be freed before Christmas, and said that an official U.S. investigation into alleged crimes of the deposed shah would be a "very positive step" that could end the 45-day crisis.

Foreign Minister Sadegh Ghotbzadeh said in an interview that his scaled-down demands for the release of the hostages carry the "full authority" of Iran's ruling hierarchy and are "already cleared from many angles." He repeated twice that he was using this interview to signal Washington on ways to end the impasse that has dragged on for more than six weeks.

The call for a full probe by the American government into relations with Iran since the 1953 CIA-backed coup that returned the shah to power was a far cry from the original demand that the deposed shah be returned in order to secure the hostages' release.

While the students still maintain that demand, other Iranian leaders have steered further and further away from it as the hostage crises drags on and as the realization grows that the United States could not and would not return the shah.

The foreign minister does not have the final word on policy decisions in a country whose power is divided among the radical students holding the U.S. embassy, the Revolutionary Council which is nominally in charge, and Ayatollah Ruhollah Khomeini, who is the religious and political leader.

Khomeini, for example, today repeated the demand that the United States return the shah even though he is now in Panama, a country the religious leader said is controlled by America.

Significantly, however, for the first time in 45 days Khomeini's demand for the return of the shah was not linked to the fate of the hostages, who were not mentioned in his talk.

As a gesture to spur the U.S. decision on an investigation, Ghotbzadeh said Khomeini had decided to allow the hostages gifts from their families, Yule trees and Christmas Eve services conducted by Catholic and Protestant ministers, who will also serve as the long-sought independent observers to certify the good health of the 50 Americans.

"That is the gesture that we make to disinflame the public opinion" in America, he said.

As welcome as the holiday services may be, the clergy are not the same as the delegation of independent international observers, including a doctor, that the United States has demanded be allowed to see the hostages. These demands have been brought to the Foreign Ministry by diplomats here who have volunteered to perform service.

Ghotbzadeh said authorities here have not thought about allowing news correspondents or television cameras into the embassy on Christmas Eve so that the American public can see for themselves the condition of the hostages. t

Ghotbzadeh indicated that authorities here had been considering a "particular case" for pre-Christmas release, but he declined to reveal any details -- including why the release fell through, how many Americans were involved and how this "case" differed from that of the rest of the hostages.

Diplomats here have said they have been trying to arrange for the release of three Americans who are reported to suffer from chronic heart or circulatory ailments.

Ghotbzadeh, though, insisted that none of the hostages -- whom he once called "prisoners" in a slip that he immediately corrected -- "feel slightly bad in any way."

Ghotbzadeh's retreat from his statement Sunday, which raised the possibility that some of the hostages could be home for Christmas, vividly illustrates his lack of control over the embassy militants. The students have steadfastly maintained that no hostages would be released until they all face spy trials, and said today that the foreign minister has "gone over the limits" in statements about the hostages.

During today's interview, Ghotbzadeh left vague what kind of investigation the United States should conduct, and whether it must get under way before any of the hostages can be released.

At one point he mentioned a congressional probe, similar to the ones that sparked the national debate on America's involvement in Vietnam. But he emphasized that some assurance of government action is needed by Iran. b

If the hostages are released without the promise of a serious investigation, he said, U.S. government officials, "will bury the more general issues" -- which he listed as including CIA involvement in Iran, the wealth of the shah, the sale of unneeded military equipment to Iran and the alleged bribery of American officials by Iranian diplomats.

He also said Iranian authorities will supply material to aid the U.S. government probe and suggested that newspapers use the Freedom of Information Act to get documents to show what the CIA has done in Iran.

Ghotbzadeh said word of American investigations into what he considers the real issues separating the United States and Iran -- the alleged crimes of the shah -- could be used as leverage to persuade the students to give up the hostages.

"Those things," he said, "will at least give a certain impression here that the American government is really trying to do something about the real case."

Ghotbzadeh's suggestion, however, presents problems for the United States which must decide how to respond in a positive way without appearing to be giving in to extortion.

The foreign minister, a long-time close aide of Khomeini, visited the 79-year-old religious leader Monday in the holy city of Qom. Ghotbzadeh said they talked about general foreign policy issues, including the outline of policies regarding the hostages.

"I am talking with full authority and I know what I am talking about," said Ghotbzadeh, referring to the charges of the radical students that he is speaking out of turn.

What is important for Iranians, Ghotbzadeh said, is for the United States to realize that "behind the question of the hostages is the question of the shah."