Iran's foreign minister said tonight that all 50 American hostages being held at the U.S. Embassy here will be forced to appear before an international tribunal, which he called a "grand jury," to see if they have been guilty of spying.

"Unless they appear before the grand jury, no one knows if they are guilty or not guilty," Sadegh Ghotbzadeh told reporters.

Earlier, on NBC-TV's "Meet the Press," he said this international tribunal will be formed to investigate "American interference and wrongdoing in Iran" since the 1953 CIA-sponsored coup that returned the shah to power. He said he hoped the tribunal could be formed within 10 days.

Ghotbzadeh said he wants the tribunal to be formed as soon as possible so "at least we can release some who are not guilty."

In Washington, meanwhile, the White House announced that President Carter has sent Attorney General Benjamin Civiletti to the Hague to present the American case against Iran to the International Court of Justice, whose public hearing begins tomorrow on a U.S. request for an interim order directing Iran to release the 50 hostages immediately.

["In light of the importance and urgency of this case, the president has asked the attorney general personally to present the position of the United States to the court," the White House statement said.]

Ghotbzadeh's statements today did not appreciably clarify the prospects of the hostages, who alternately have been threatened with trial by Islamic courts and by the "student" militants holding them.

The foreign minister reiterated his Friday promise that international observers would be allowed to see the hostages, but he did not specify when. And, although he acknowledged that he has not seen the hostages himself, he nevertheless said they are "fine, in good health, comfortable."

He denied that any of the captives are being brainwashed and insisted that when the neutral observers saw them, "You'll realize all the propaganda [about the poor health of the hostages] against us is false."

Repeating his Friday statement, which had been denied immediately by the embassy captors, he said, "Those not guilty of spying cannot be held forever. The release of the hostages not involved is coming, but the date cannot be fixed with certainty." The militants have insisted that all hostages face trial.

The release of the hostages found guilty of spying "depends on when the shah is returned to Iran," he insisted today.

While the U.S. government has said the international tribunal is unacceptable, observers see it as a way for Iran to release at least some of the hostages quickly while focusing widespread public attention on what it believes are the major issues -- the crimes of the shah and U.S. interference in Iran.

The tribunal is also seen as a way to defuse the anger of the students holding the embassy. Ghotbzadeh told reporters tonight the militants are becoming increasingly restive as time goes on without the United States returning the shah and with world opinion turning against them for taking diplomats hostage.

There was no indication here, meanwhile, that the special envoys from Europe and the Middle East countries have arrived in Tehran to argue the U.S. position with Iranian authorities.

Reports from Washington yesterday indicated that these envoys carrying details of a proposed U.S. deal for release of the hostages, had begun to arrive in Iran. The deal was said to involve release of hostages coupled with an international tribunal to investigate the crimes of the shah.

Diplomats from European and Moslem nations said they know nothing of any special mission coming here, but then they pointed out that success of any such mission depends on its ability to conduct negotiations in secret.

Ghotbzadeh said the idea of an international tribunal was not brought to Iran by any outside envoy but was developed here.

[In another development, special correspondent Michael J. Berlin reported from the United Nations that Secretary General Kurt Waldheim spoke by phone with Ghotbzadeh. A U.N. spokesman said the foreign minister agreed to Waldheim's request that he receive Sri Lankan Foreign Minister Said Hameed, who arrived in Tehran Sunday, and a Lebanese employe of the U.N. Development Program, Zohair Yammin, who is expected in Tehran shortly and will be Waldheim's new channel of communication with Iran.]

Ghotbzadeh complained once more about the basic difference between U.S. and Iranian positions: the U.S. only wants to discuss the freeing of the hostages while Iran thinks the only issue worth talking about is the return of the shah. Ghotbzadeh tonight repeated his call for a "gesture" showing that the American government and the American people understand what he called the crimes that the shah committed and the role of the United States in Iranian affairs.

He did not, however, specify what type of gesture he is looking for, nor did he say that any gesture that he considers satisfactory would lead to the release of all the hostages.

Ghotbzadeh said most of the information provided to the international tribunal, which will be composed of individuals from Iran and other nations who would be able to vote as their consciences dictate, would come from documents found at the U.S. Embassy.

These include papers that the students holding the embassy say prove that three of the hostages are CIA agents operating under diplomatic cover. Another document is a memorandum from the defense attache, who is also a hostage, saying that visa preferences should be given to top Iranian officials who provide intelligence information.

Ghotbzadeh said Iran wanted to "normalize relations" with the United States soon after the shah was toppled last February, but "even that was not honored." He said documents found in the embassy showed the United States is still trying to interfere in Iranian affairs.