Secretary of State Edmund S. Muskie said yesterday that indirect negotiations with Iran seem to be entering "a new phase," but he said it remains as uncertain as ever whether the 52 American hostages will be released soon.

In the face of conflicting signals and press reports from Tehran, Muskie declined to express confidence about the future course of the diplomatic maneuvering on the hostage issue, saying it is not clear to him at this point that the Iranian authorities have indeed produced their final position.

Muskie's statement on NBC's "Today" show reflected concern among American officials that the new Iranian position -- expected to be transmitted to Washington within the next few days- may pose demands which are difficult or even impossible for the United States to meet.

The United States is waiting to hear, according to the secretary of state, whether the Iranians fully understand that the existing American proposals represent "the limit of what we can do," and whether Iran will accept them as a settlement of the hostage-related issues. "Until we know the details [of the new Iranian position] we really don't know whether they're asking us to go beyond where we've said we can go," Muskie said.

One of Iran's senior leaders, Ayatollah Mohammed Beheshti, told a press conference in Tehran yesterday that "some necessary corrections" to existing U.S. proposals will be submitted. Beheshti, who heads the dominant Islamic Republican Party, characterized the U.S. proposals as "nearly an acceptable answer" to the conditions laid down by the Iranian parliament, or Majlis.

Beheshti did not specify the proposed "corrections." On Tuesday, Prime Minister Mohammed Ali Rajai said Iran is preparing to ask for unspecified "financial guarantees" which, if provided, will result in immediate release of the hostages.

Reports from Tehran by both The Christian Science Monitor and Swedish radio, attributed to diplomatic sources there, said Iran is preparing to harden its demands in ways which would make release of the hostages in the near future unlikely. The reports said Iran is planning to demand that the United States transfer the wealth of the late shah, Mohammad Reza Pahlavi, to non-American banks in a third world country, perhaps Algeria.

U.S. officials said they had no indication that Iran is preparing to make such a demand, saying that nothing in the recent diplomatic dialogue seemed to set the stage for it. The Washington sources said such a demand would be impossible for the United States to meet, and thus would signal a decision in Tehran against a diplomatic settlement of the hostage issue in the foreseeable future.

The stories from Tehran also said that the United States recently provided Iran with 18 signed but undated presidential decrees to implement the actions which have been promised by Washington in the context of the hostages' release. U.S. sources characterized this as much exaggerated account of a part of the recent manuevering.

The U.S. negotiators apparently did give the Algerian intermediaries several sample presidential orders, reportedly far short of 18, illustrate in tangible detail the actions which can be taken upon the release of the hostages. Washington sources denied that any signed presidential orders were involved.

As of last night, according to Washington officials, there was still no word from Tehran when and how the latest Iranian proposals will be presented.

In the meantime, the State Department confirmed, work is continuing through diplomatic intermediaries to arrange a Christmas observance for the hostages, in case they are still in captivity a week from now.