Iran yesterday proposed a mechanism for breaking the deadlock over the American hostages, saying that Iranian gold and other assets frozen by the United States should be transferred to the Algerian Central Bank before the captives are released.

The proposal was contained in a detailed revision of the four conditions for freeing the 52 American hostages. The revision, sent by Tehran to Washington yesterday through Algerian intermediaries, included guarantees for both countries in addition to the proposed mechanism for handling the complex problem of the frozen Iranian assets and American claims against them.

"For the first time," one U.S. government source said yesterday, "we have a complete proposal."

In Tehran, Iranian officials outlined the proposals following the departure of a team of Algerian diplomats to convey the latest Iranian message to the hostags issue to the United States.

The major change from the original conditions approved Nov. 2 by Iran's Majlis (parliament) is a proposal that the United States "deliver to the Algerian Central Bank the Iranian government's expropriated gold and assets," according to a statement by Executive Affairs Minister Behzad Nabavi, the head of a special Iranian hostage commission. The statement was given to Iran's official Pars News Agency and broadcast by Tehran radio.

Under the original conditions, Iran demanded that the funds be released and "put at the disposal of the Iranian government."

Under Iran's latest plan, that transfer to the Algerians of the more than $8 billion in Iranian assets that President Carter froze in response to the seizure of the hostages would have to take place "prior" to their release, according to Nabavi's statement.

Nabavi also said Iran "has accepted a form of arbitration acceptable to both sides for the investigation of the claims of the parties."

Nabavi linked the turnover to Algeria of the frozen assets to the investigation and arbitration of the claims. His statement has led observers to believe that some form of international claims commission, based in Algeria, is part of the new proposal.

In an interview reported in The Washington Post on Nov. 5, the head of Iran's Central Bank, Ali Reza Nobari, said his country was prepared to pay its debts to American banks and corporations that had filed claims in U.S. courts against the frozen Iranian assets.

Nobari added at that time that "an escrow account" could be established in a third country and that any judgments approved by an international claims commission could be paid from the money put aside.

The new idea that the frozen assets would be placed in Algeria's Central Bank fits into the proposal outlined a month ago by Nobari.

In the initial set of conditions, Iran demanded that all the U.S. claims against Iranian assets be dropped. There was no mention of any investigation of those claims or any arbitration.

Nabavi also said that the proposals sent to the United States through the Algerians yesterday were the "final reply" on the matter. Other Iranian officials, however, have made similar public statements about the two earlier messages on the release conditions sent to Washington.

Given the infighting between Iranian political forces now under way, neither the government nor its critics can appear to be negotiating over the conditions for the hostages' release that were first set forth on Sept. 12 by Ayatollah Ruhollah Khomeini, Iran's revolutionary leader.

The conditions were: a U.S. pledge not to interfere in Iran's internal affairs; unfreezing of the Iranian assets; cancellation of all claims and lawsuits against Iran; and return to Iran of the wealth of the shah and his family.

Iran and the United States now have had two exchanges on the conditions in the quasi-negotiations that use the Algerians as intermediaries. At the end of the first exchange, Iranian and U.S. officials said there was agreement "in principle" on the four conditions as the basis of discussion, but implementation has always been a sticking point.

Yesterday, Nabavi said the latest U.S. plan had "been recognized as generally acceptable." But he added that "the guarantee of these undertakings . . . must first be completely assured."

He said that "written promises with the signature of the U.S. president are not sufficient" and that only the transfer of Iran's assets would be satisfactory.

Nabavi raised the possibility that there may be additional negotiation over U.S. pledge of noninterference in Iran's affairs, a point that both sides had said earlier had been settled. The Iranian official said Washington's "statement" on this subject must be revised to "accurately tally with what the Majlis has sanctioned."

One U.S. official who has read the latest Iran message said it has "some worse and some better" positions than those previously exchanged. He would not say whether this was one of them.

On the question of returning the assets of the shah and his family, Nabavi said, "Acceptable guarantees as goodwill for a proper implementation should be given to the Algerian government."

That, too, could represent a significant change from the earlier demand that the president declare those assets the property of the Iran government and "take all legal and administrative actions necessary to transfer those properties to Iran."