The United States has accepted Tehran's latest proposal for settling the outstanding loans from American banks to Iran -- an issue that has been a principal obstacle to an agreement for the release of the 52 hostages, it was learned late yesterday.

There was no public comment in Iran on this development, which was disclosed here by American sources. The Iranian government yesterday twice requested unspecified "clarifications" on the general "issue" of the transfer of its frozen assets. It was not known if Iran's questions referred to the bank settlement, which apparently was reached Friday, or to some other aspect of an overall agreement to free the hostages.

In all, the United States has frozen $6 billion in Iranian deposits, $2 billion in banks in this country and $4 billion in European branches of American banks.

Under the banking settlement, the United States would unfreeze the $4 billion now being held abroad and transfer that money to an undisclosed third country central bank. At the time the hostages are released -- sometime before Tuesday -- those funds would go to Iran.

Iran, in turn, would use about $1 billion of that money to repay American banks in full for the loans they had made directly to the government of the later former shah.

Another nearly $2 billion of the $4 billion would be placed in an escrow account and used to pay off the remaining loans by American banks to Iranian institutional borrowers, such as development banks, and Iranian companies.

The American banks have agreed to a procedure, requested by Iran, for validating the legality of this latter group of loans. The escrow account, sources said, will be more than sufficient to cover all these loans.

"The financial aspects are all set," one American banking source said. But a top government official cautioned that "there are details still left to be worked out."

The government official did say that Iran has agreed in principle that final transfer of the $2 billion in frozen Iranian bank deposits in the United States will take place after the hostages are freed. The United States will guarantee, however, that these funds will be released as soon as the mechanism for an international claims commission is established.

The net effect of this compromise would be to leave Iran, at the time of the hostage release, with less of its money than it has publicly demanded.

U.S. government officials insist, however, that the Iranians understand this and agree to it.

Although the Tehran regime has yet to approve publicly all aspects of the financial package built around the Iranian bank settlement proposal, financial experts and lawyers representing Iran's central bank, the U.S. Federal Reserve, the American commercial banks, and the Bank of England are drawing up a series of agreements in London to implement these moves.

This unusual step -- drawing up the complex legal and financial papers to implement this approach before the terms have been agreed to by the two countries -- has to be taken, sources said yesterday, because time is fast running out on the Carter administration's authority to enter into such an arrangement.

One lawyer involved in the discussions said yesterday it is doubtful the technical documents necessary for any other approach could be put together in time to permit implementation before noon on Jan. 20, when President Carter leaves office.

One source on the Iranian side of the discussions yesterday put forward a word of warning that other minor details, some associated with the frozen Iranian assets and other relating to the return of the assets of the former shah and his family, remain unresolved.

"We hope they will be handled later after the hostages release," he said.

As an example, this source noted that the group working in London has deferred until after the hostage release settlement of the question of what interest payments the Iranians should receive on their deposits that have been frozen in the American banks.

The framework for the compromise agreement now being hastily put together grew out of a declaration of four conditions made by Ayatollah Ruhollah Khomeini on Sept. 12. He demanded a pledge that the United States would not interfere in Iran's internal affairs; the unfreezing of Iran's assets; nullification of all legal claims against Iran, and return of the fortune "stolen" by the shah and his family.

Negotiations using Algerian diplomats as intermediaries have been going on since early December. But it was not until an Iranian note was received in Washington Dec. 19 that the Tehran government made its first attempt at a concrete, detailed basis for implementing Khomeini's conditions.

The note listed $9 billion worth of frozen assets that consisted of the bank deposits, accounts payable by American companies, a Pentagon trust fund, and holdings of the Federal Reserve Bank in New York. The note also mentioned the 1.6 million ounces of Iranian gold in the Federal Reserve Bank in New York and another unidentified $4 billion in assets. The Tehran government demanded return of all these items before it would release the hostages.

On its side, the Carter administration told Iran in December that it could turn over to Iran at the time of a hostage release only the holdings of the Federal Reserve Bank in New York ($1.5 billion in securities and the gold), and possibly the $4 billion in frozen deposits held by the American banks abroad.

Although it didn't say so, the Carter administration had decided that it could not release the $2 billion in deposits in the United States because they had become involved in legal action by American companies and individuals who were seeking money from the Khomeini government.

If the compromise now being drawn up in London goes through, and these $2 billion in Iranian deposits in the United States are transferred to Iran, the American claimants will have lost their main source of compensation should their claims be upheld by American courts.

However, in another part of the proposed American-Iranian agreement, both sides have already approved an international arbitration for such claims with Iran putting up a $1 billion escrow account to cover payment of any awards.

American banks proposed the idea of Iran paying of all its outstanding loans according to an Iranian source, during informal talks several months ago. Thanks to a regulation of the U.S. Treasury implementing the president's freeze order, the American banks had in effect already paid themselves off with frozen Iranian assets.

The regulation permitted them to "set off" any defaulted Iranian loans they had made using frozen Iranian funds on deposit with their banks.

Since the freeze effectively prevented Iran from making payments of any of its American loans, all its loans went into default and were promptly paid off using frozen deposits.

Thus when the American bankers and the Iranian central bank held their discussions, the Americans had an advantageous position thanks to the freeze.

That first idea for leaving the loans paid off -- as the "set offs" had done -- was dropped when Iran's representatives initially came back with a proposal to bring the outstanding loans and bank deposits back to the situation that existed on the day before President Carter ordered them frozen. In addition, Iran would then bring them current by making the necessary principal and interest payments.

The American banks responded by saying they would agree to that approach, but only if they had guarantees from Iranian government and its central bank that all the loans would eventually be paid off. To insure that would happen, the banks also wanted Iran to set up an escrow account to cover future payments.

In December, Iran agreed to establish the escrow account, but added -- ominously in the minds of some American bankers -- that it reserved the right to review the legality of all the loans before payments were made.

Discussion over the last few weeks had been hung up on terms for protecting the American loans, until last week when Iran suddenly offered its last suggestion.

Many of the banks have filed lawsuits against the Iranian government for the amounts of their loans, despite the "set off" device. Once the loans are repaid, presumably these suits would be dropped. According to some reports, the banks have agreed to drop the suits prior to final repayment.