An air of new optimism became evident in U.S. government circles last night that a break might come soon in the stalemate over the American Hostages in Iran.

The attitude developed as Iranian Foreign Minister Sadegh Ghotzbadeh predicted that the hostages, held by militants in the U.S. Embassy compound in Tehran since Nov. 4, would "soon" be turned over to the control of the Iranian government.

This new sense of hopefulness followed a weekend of confusion over claims by Iran that President Carter had sent conciliatory messages to Iranian leaders.

White House press secretary Jody Powell denied Saturday and again yesterday that Carter had sent messages of the type described by the Iranians. But what seemed at first like unequivocal denials on Powell's part turned out to be narrowly phrased to deal only with the purported content of the U.S. messages as put forward by Iranian officials.

These messages -- whatever their precise content -- seemed to be the basis for the belief in Washington that hopeful developments were likely in Tehran.

Ghotbzadeh said as much in an interview with American television yesterday. He called Carter's purported statements "helpful" in terms of clearing some of the tensions and suspicion that have existed between the two countries.

Ironically, the things Ghotbzadeh claimed Carter had said were the same things denied by Powell as not having been communicated to anyone in Iran. But the Swiss government confirmed yesterday that it had delivered a message from Carter last Wednesday to Iranian President Abol Hassan Bani-Sadr.

Powell replied in essentially the same terms he used Saturday. He said: "Neither the president nor any other American official has sent such a message to Khomeini or any other Iranian official."

On the surface, his words again seemed like a flat denial that any high-level communication had been sent. However, authoritative sources, when asked later about the apparent disparities in the various accounts of what had happened, pointed to such phraseology in Powell's statements as "such a message," "such a letter" and "any such statement."

These phrases, the sources noted, had the effect of limiting Powell's public denials to the Iranian account of the message from Washington. The Carter Administration, the sources asserted, still stands by its contention that the Iranian description of the message's contents was inaccurate.

One source, while conceding that messages had been exchanged between the governments, contended that it was inaccurate to say that the disputed communication came directly from Carter. That source predicted that the Swiss government soon will change its original story that it acted as a courier to take a message from Carter to Bani-Sadr.

Some of the sources hinted that the White House's silence might be tied to newly awakened hopes that the Iranian government might be on the verge of a showdown with the militants holding 50 hostages in the U.S. Embassy compound.

This version was given some credence by reports from Tehran last night that, after a meeting of the Revolutionary Council there, Ghotbzadeh said the council would move "soon" to take custody of the hostages away from the militants.

Powell also implied that some major move affecting the hostages might be in the works. At a Milwaukee press conference, he said:

"It is my belief that for me to become involved in a detailed discussion of what messages may or may not have been transmitted would be deleterious at this time . . . This is a period of some ferment."

He added that he believed things "would become clear over a later point," possible within the next day or two. But he refused to elaborate.

Other sources said the administration simply was not willing to make the kind of concessions implied by the Iranian version of what the message said. One very authoritative source said there was a belief among some administration officials that the Iranian account might have been the product of one or more leftist French lawyers, who have been advising Bani-Sadr on ways of resolving the hostage crisis.

One of these lawyers, Christian Bourguet, is believed to have had contacts with White House chief of staff Hamilton Jordan in Europe and possibly in Panama last week when both were involved in the controversy over deposed shah Mohammad Reza Pahlavi's flight to Egypt.

There is a suspicion that Bourguet has served as a conduit for passing messages between Washington and Tehran, and some of the speculation about the current controversy has centered on whether he had a role in passing Carter's alleged message to Bani-Sadr. According to one U.S. source, Bourguet and his associates might have suggested to the Iranians the version they revealed Saturday as a way of signaling Washington about the outlines of a solution acceptable to Tehran.

Some of the ideas that the Iranians say Carter proposed in the message are known to have been under consideration by the United States last month.But Washington's willingness to explore those approaches at that time were tied to hopes that the now-suspended United Nations commission initiative would succeed in getting the hostages transferred from custody of the militants.

Under the terms of the U.S.-Iranian deal that created the U.N. commission, such a transfer of custody would have prepared the way for Carter to make some statemate satisfying Bani-Sadr's demand that the United States acknowledge its past actions in Iran and promise not to intervene in Iranian affairs in the future.

Similarly, at the time negotiations on creating the U.N. commission were under way, the United States is understood to have signaled its willingness to seek a means of "normalizing relations" with Iran after the hostages were freed.

Both of these ideas -- an implied willingness to admit past U.S. actions and a joint commission to seek normalization of relations -- are contained in the Iranian account of Carter's alleged message.

However, when the U.N. commission failed to achieve transfer of the hostages, the United States put on hold its willingness to pursue these ideas further. Reliable sources insisted last night that Carter remains unwilling to follow up on any of these steps as long as the hostages remain in the hands of the militants.

In fact, the administration has been moving toward a renewed get-tough stance and is expected this week to announce a series of limited economic and political moves against Iran.

One subject that remained confused last night was precisely how the disputed U.S. message was transmitted to Iran. From the evidence that became available yesterday, a number of exchanges have taken place between the two governments recently.

Ghotbzadeh, interviewed on the television program "Issues and Answers" (ABC, WJLA), said the message was conveyed to him and Bani-Sadr orally and that he translated it into the Farsi language and gave a written version to Khomeini.

But the Swiss foreign ministry in Bern said yesterday that the message delivered to Bani-Sadr by its embassy in Tehran last Wednesday was written. In addition, the Associated Press quoted a foreign ministry spokesman, Hansjoerg Renk, as saying that Swiss Ambassador Erik Long had delivered a second written message to Bani-Sadr yesterday.