Initial hopes for a quick release of the 52 American hostages following the U.S. response to Iranian conditions for freeing them now seem to have been replaced by the possibility of further extended negotiations, according to sources in Tehran and Washington.

The debate over how to reply to the United States now is centered within the office of Iranian Prime Minister Mohammed Ali Rajai amid indications in both capitals that the likely result will be neither outright rejection nor acceptance, but rather further bargaining.

A broadly based Iranian government committee, including representatives from the Majlis, or parliament, Iranian President Abol Hassan Bani-Sadr's moderates and the Western-educated technocrats, had been meeting on the still-secret American proposals since last Thursday.

This group now has turned the matter over "to people in the prime minister's office to arrange for a response," one top Iranian official said yesterday in a telephone interview from Tehran. o

But it was also learned yesterday that Rajai's office was still seeking clarification of portions of the complicated American plan -- another clue that no final Iranian position has been reached.

These moves -- consolidation of power within Rajai's office and reaching out for additional information -- represented to observers the first signs that the two countries are moving toward some form of ongoing negotiations.

Although there are no direct discussions between Iranian and American officials, several channels for communication appear to exist. They include both American and foreign lawyers employed by the Iranian and the Algerian diplomats who delivered the U.S. proposals to the Tehran government last Wednesday.

American officials recognized that the Carter response would "not meet the literal interpretation of [the Iranian] demands," one source said yesterday.

The hope of the U.S. drafting team was that if the Iranians did not accept it, they would say -- publicly or through the Algerians -- that "it was unsatisfactory in the following ways . . ." instead of turning the whole package down, this source continued.

Two sections of the American plan -- dealing with Iranian demands for return of the shah's wealth and unfreezing of the more than $8 billion of the Tehran government's blocked assets -- were used yesterday in interviews with both Tehran and Washington sources to illustrate the type of gaps between the two countries.

An Iranian source who yesterday said he was "not optimistic" about the current situation declared that the United States had "not made any concession" on the issue of the shah's wealth. He said Washington proposed only to help Iran press its claims in U.S. courts but that it was up to Tehran "to prove it was ours."

Iran, he said, wanted the U.S. president to recognize the nationalization of the shah's assets and those of his immediate family. That act, he said, would aid in any court action.

U.S. officials maintain that such a step by the president would cause political problems in other situations and that it would lead to extended legal actions.

The Carter proposal, other sources insisted, included additional suggestions on what Washington could do that would be helpful in pressing Iran's claims for the shah's money.

On the frozen assets, the Iranian source said the Carter program would guarantee immediate release of only the $2.5 billion in gold and U.S. Treasury bills held in the Federal Reserve Bank of New York and possibly additional funds held in a U.S. bank in England. It would not, however, guarantee release of more than $10 billion in additional assets that the Iranians claim are in U.S. hands.

Again, however, the U.S. proposals suggest additional means to get at the frozen funds, sources said.

The Iranian official said the Carter proposal failed to accept the Iranian legal notion that the claims and other lawsuits filed against Iran could be removed at the order of the president. These claims currently tie up billions of dollars in frozen Iranian assets.

"No American lawyer believes that approach would work," a Washington official said yesterday. Other sources said the U.S. proposal offered another way to solve the claims problem, including the possiblility of an international commission -- an idea first suggested by the governor general of Iran's Central Bank, Ali Reza Nobari.

The Iranian official was also critical of the U.S. response because it made no mention of shipment to Iran of the spare parts and military equipment that the Tehran government had ordered and paid for before the freeze.

A Washington source acknowledged that the spare parts and military equipment were not mentioned in the U.S. proposal, but added that "they were not included in the Iranian conditions. And we responded only to their proposals."

Sources in both Tehran and Washington seemed to agree yesterday that if negotiations get bogged down, they could last a long time since neither country was under great pressure to reach a quick solution.

Although President Carter once said that the Iraqi-Iranian war created an incentive for the government of Ayatollah Ruhollah Khomeini to solve the hostage problem, sources in both capitals yesterday said that did not seem to be the case.

Although it is clear that Tehran had decided that the time had come to work out a hostage release -- beginning Sept. 12, with Khomeini's enunciation of Iran's four conditions -- U.S. officials now agree that the Iranians are "far from a point where they have no other choice but to settle on U.S. terms," as one Washington source put it.

The U.S.-held spare parts would probably help the Iranian war effort, but the war is so desultory that they are not a necessity. "And shipments from North Korea and Eastern Europe are meeting their needs," according to U.S. officials.