With real estate values crashing, the Federal Reserve Board is looking for a quick way to get banks to start making loans again, Fed Chairman Alan Greenspan told a congressional panel yesterday.

The "severity" of the recession is a matter of "considerable concern" at the Fed, said Greenspan. In addition to weighing further cuts in interest rates, he said, the Fed is considering other ideas to confront the credit problem and "restore a modicum of rational lending where you're dealing with creditworthy customers."

Greenspan made his comments before the Senate Banking Committee, which was told yesterday that $77 billion will be needed through the end of this fiscal year to cover escalating costs of the cleanup of the nation's failed savings and loan institutions. Greenspan is a member of the board that oversees the Resolution Trust Corp., the agency charged with dismantling and selling off failed S&Ls.

Another member of that panel, Treasury Secretary Nicholas F. Brady, told the committee that the cost of the thrift cleanup has crept to the upper end of the $90 billion to $130 billion range the administration estimated last summer. But, he said, investor skittishness due to the Persian Gulf War, crashing real estate values and the credit crunch are "volatile variables" that could drive the cost up further.

Senators listening to yesterday's testimony warned that the administration could not have a "blank check" to deal with the thrift cleanup, but there were indications that they were prepared to approve the specific funding request.

While the problems in the nation's thrift institutions were the reason for yesterday's meeting, Greenspan's remarks quickly moved to embrace the current recession and parallel problems in the banking system.

Greenspan said several ideas are under discussion to address the problem of tight credit, but he said he could not discuss them because that could affect the financial markets. He said, however, that "time is not on our side."

Several congressional sources interpreted Greenspan's remarks as hints that direct aid to banks is under consideration or that there has been a shift in thinking on bank mergers.

Greenspan said many banks are not making new loans as they try to shore up their capital base.

As a result, they are losing customers and getting pushed out of the marketplace by stronger banks.

Greenspan said another "question that's got to have our attention" is the way real estate is valued.

More and more, he said, values are based on what the property would bring at an immediate liquidation sale, instead of what it would bring as a long-range investment.

New England senators, including Sen. John Kerry (D-Mass.), urged Greenspan to act promptly to ease the pressure on banks there to contain what he described as an economic "meltdown."

"We are hemorrhaging badly, badly in New England ... and it's going to spill over to the rest of the country," said Sen. Christopher Dodd (D-Conn.).

The credit crunch and the steep decline in real estate values are making it harder and more costly for the RTC to dismantle failed S&Ls, RTC oversight board members said.

The estimated size of the thrift losses, put at $50 billion when the S&L reform legislation was enacted in 1989, has been climbing dramatically.

The RTC is asking for immediate congressional approval of $30 billion more to cover losses in the current fiscal year, and it expects to spend another $47 billion in borrowed working capital this year.

The RTC has already used $53 billion in working capital -- funds that it hopes to recover eventually as thrift loans, real estate and securities are sold off. Without the funds, Brady said, the RTC would be unable to close insolvent thrifts.

Allowing those institutions to continue to make risky loans could drive up the ultimate cost of the cleanup $750 million to $850 million a quarter.

Congressional refusal to act on the funding issue during the 1990 session has caused the RTC to slow the pace of thrift closings during the first quarter of 1991, resulting in an estimated cost of $250 million to $300 million.

The Congressional Budget Office, in a letter to committee Chairman Donald W. Riegle Jr. (D-Mich.) released yesterday, said it found merit in the argument that money could be saved if all seriously ailing thrifts were shut down immediately instead of over time.

The CBO said it could not quantify the size of the savings, but a Brookings Institution economist has estimated savings of $12 billion.