The United States yesterday transferred Iranian-owned securities to cash in preparation for an agreement, possibly as early as today, for release of the 52 American hostages.

The actions were ordered by President Carter as senior administration officials met with executives of 12 American banks to formulate a U.S. response to Iran's latest proposals for settlement of the 14-month hostage crisis.

The American response, forwarded to Tehran overnight, is in the form of an international agreement between the two countries, according to White House press secretary Jody Powell. "If they accept it, we will have an agreement," he said.

Powell and other officials cautioned that Iranian acceptance is not certain, especially in light of the many disappointed hopes of the past months. Adding to the uncertainty are statements from officials in Tehran insisting that financial issues are already resolved. In Washington this was denied.

Nevertheless, there was a keen sense of anticipation, including rare public expressions of optimism, that freedom for the captive Americans may be the last and most spectacular event of the presidency of Jimmy Carter, who gives up the office to Ronald Reagan at noon Tuesday.

Reagan, who in recent days had refused to give what he called "a blank check" for any agreement to be made by Carter, said yesterday that, as he understood the details of the proposed deal, "I thought that [they] made sense . . . . I continue to be optimistic."

The timetable for a settlement remained uncertain as the clock ticked toward the end of Carter's term, but officials said the proposed agreement, drafted by the United States yesterday, should reach Tehran by Saturday morning. Iran time (late Friday night here). If Iran promptly accepts the agreement, it is likely to be announced by Carter sometime today.

Following an agreement, the Iranian gold and some of its other financial assets previously frozen by presidential order will be transferred to the hands of a third party. New York bankers said it would be difficult, though not impossible, for some of the Iranian money to be transferred out of the U.S. banking system before 9 a.m. Monday.

It was not clear whether the third party would be algeria, which has acted as the intermediary in the indirect negotiations of recent weeks, or another country.

The Iranian gold and assets would be returned to Tehran's control simultaneously with freedom for the captive Americans.

There were unconfirmed reports that the hostages might be flown to Algiers as the first stop on their journey home. Whether or not this is the case, U.S. officials continued to make plans for the hostages to be transferred to the U.S. Air Force hospital in Wiesbaden, West Germany, for three to five days of recuperation and medical attention.

In response to questions, Powell would not rule out the possibility that Carter might fly to Germany to meet the hostages.

After their stay in Germany, they are to be flown to a private reunion with their families somewhere in the United States. Eventually, the hostages are to come to Washington for a formal welcoming ceremony.

Even if all goes without a hitch -- and it rarely has so far in the long-running international drama -- officials did not expect that the hostages would be in Washington before next weekend, at the earliest.

All this remained hope, rather than fact, as lights burned brightly at the State Department last night, where the representatives of 12 of the nation's largest commercial banks pored over the complicated legal and financial details of the remaining assets issues.

Among those participating in the meeting were Secretary of State Edmund S. Muskie, Treasury Secretary G. William Miller and former White House counsel Lloyd Cutler, who now is serving as a special adviser to Carter.

A similar meeting, involving a team of U.S. experts headed by Deputy Secretary of State Warren M. Christopher, was going on in Algiers with the London branch managers of some of these American banks.

Christopher and the Algerian Foreign Ministry were the central transmission points for a series of messages between Washington and Iran over the past day, since Tehran Thursday dispatched its answer to the most recent U.S. proposals for settling hostage-related issues.

The State Department said these messages were questions and clarifications, back and forth, rather than a definitive of agreement.

The language of the final version of the proposed executive agreement between the United States and Iran was being drafted primarily by the Christopher group in Algiers, officials said. They said Iran had requested that the latest U.S. response be made in the form of an international agreement ready to be signed.

Because time is running out for the Carter administration, which previously had set an informal deadline of yesterday for an agreement that could be implemented before Inauguration Day, it is likely that any agreement would be sealed "electronically by an exchange of cabled messages rather than by signatures on a common document, according to State Department sources.

The outline of the present U.S. proposals, as made known in Washington, falls far short of Iran's previous demand, made on Dec. 19, for the deposit with Algeria of $24 billion in gold, cash and other "guarantees" to ensure the return of Iranian government assets and the wealth of the late shah Mohammad Reza Pahlavi.

The two main categories of Iranian assets to be transferred immediately in connection with the hostage release, as now envisioned, are about $2.2 billion which has been held by the Federal Reserve Bank of New York, and more than $4 billion deposited in the European branches of American banks.

It was to deal with the first category, the holdings at the New York Federal Reserve Bank, that Carter issued his orders yesterday. One order was to convert about $1.2 billion in U.S. government securities owned by Iran into cash to facilitate the transfer. Officials said there would be no effect on American securities markets.

Carter's other order was to transfer about 1.6 million ounces of gold, worth about $1 billion, from the vaults of the New York Fed to London. No gold left American shores in this transcation, described by officials as a swap of paper placing some of the Bank of England's gold in a special account. In return, the United States assigned to Britain an equivalent amount of its gold reserves.

The central question in the talks with the commerical bankers was how to handle the problems arising from loans which had been made to Iran during the reign of the late shah. When the United States froze Iranian assets on Nov. 14, 1979, 10 days after the seizure of the hostages, the commerical banks were permitted to use some of these Iranian government funds to pay off the outstanding loan balances.

Part of the current U.S. proposal is the return to Iran of about $4 billion of its assets in the hands of the European branches of the American banks. The question is how to restore that part of these funds which has been taken to satisfy the loans.

The American bankers are aiming for the greatest degree of assurance that the old loans will not end up as losses on their books. And they have been asking for the maximum degree of U.S. government involvement in the solution, possibly a U.S. order directing their financial actions, so that the government will share responsbility for any financial setbacks and to protect themselves from stockholder suits.

The length of the meeting at the State Department, which began at 11 a.m. and continued until after 9 p.m., prompted speculation that the banks were balking at the administration's plans for a speedy solution. However, Treasury Secretary Miller said "the attitude of the banks is very constructive." He added that many technical matters needed to be ironed out.

An official of one of the large U.S. banks said, "This bank would never stand in the way of these people being released, but we are trying to get the best possible deal through the negotiators. But once the president tells us what to do, we will do it."

Vice President Mondale, explaining the difficulties involved in the financial discussions, said, "We're trying to do things in hours that would take months otherwise."

Various officials emphasized that it was still possible for the negotiations with Iran to fail. For one thing, there may still be discrepancies between the sums of money Iran expects and the sums Washington is arranging to make available.

There is also a lingering question about Iran's willingness to give up its demand for early return of the large fortune it insists the shah and his close relatives brought to the United States. American officials have expressed the belief that little or nothing of such a fortune is in this country at the present time.

In recent exchanges Iran has not repeated its demand for immediate return of the shah's wealth or a $10 billion "guarantee" of such a fund. Muskie said Thursday he believes Iran no longer plans to press this demand, but added that the United States had not been told that explicitly.

All these events took place as Carter administration officials were saying their goodbyes to friends and colleagues in Washington, preparing to return to private life. Excitement over the hostage issue combined in strange fashion with a "last day of school" atmosphere to produce an unforgettable ending to an adminstration whose final months had been dominated by the continued holding of the 52 hostages.