The Federal Deposit Insurance Corp. is being forced to close more banks and pay off their depositors because it cannot find healthy banks willing to take over failed institutions.

The cost to the FDIC of the growing number of closings is not large because most banks that cannot be sold are small, the agency's new chairman, L. William Seidman, said in an interview.

But the trend is leaving many small towns without banks, Seidman said. The failures often involve the only bank in a community, and when it fails, residents may have to travel miles to get banking services.

With bank failures running at record levels, the decline in banking services in many small towns is just one of the problems facing the new FDIC chief.

Seidman, who took over the agency in late October, said that one of his major priorities is to prepare the agency for the possibility of a failure of a large bank.

He said that a "substantial number" of regional banks are growing rapidly through interstate acquisitions. All the banks that are being permitted to grow appear to be sound, well-run institutions, he said, but the FDIC "always looks at the worst-case possibilities." The failure of a giant regional bank could pose a serious threat to the U.S. banking system.

Regional interstate banking compacts are being developed in the Southeast, the Northeast, the Midwest and the Far West. Banks in states that are in these compacts can buy institutions in other compact-member states.

For example, the three big banks in North Carolina have been on a buying spree in the last several months. By the time the purchases are completed early next year, North Carolina will have two bank companies with assets of about $17 billion each and one, NCNB Corp., with assets close to $22 billion.

Seidman noted that Continental Illinois National Bank, which was the eighth biggest bank in the country when regulators saved it from failure last year, was considered one of the soundest and best run banks in the nation until only months before it got into trouble.

He said federal bank regulators performed well in rescuing Continental, but said they had to improvise the whole way. Seidman, who was economic counselor to President Ford, said he hopes bank regulators can develop a "clear path" to follow in the event another large bank gets into trouble.

The new FDIC chairman said it is not clear why it has become so difficult to find healthy banks to take over failing ones.

"In the past, you almost always got lots of bidders" for a failing bank, he said. But last week, for example, the FDIC had to close two small banks and pay the depositors because no other banks would bid for them, he added.

"We're still getting bids for a lot of failing banks, but the number is declining. A pretty substantial percentage of bank failures during the last two months" were payoffs, rather than mergers, Seidman said.

About 125 banks -- nearly all of which are small and many of which are in rural areas -- are expected to fail this year, and a similar number of failures are expected next year as the economic crisis in agriculture continues to deepen.

As a result, a growing number of communities will face a loss of banking services unless ways can be found to increase the number of banks willing to bid on failing institutions.

Seidman said his agency, which not only insures deposits but also takes over the "estate" of a failed bank, is studying the problem of few bidders.

In some cases, he said, state laws make it hard to find bidders. Some states do not permit branching, or permit only countywide branching. It is far more expensive to take over a failing bank and set it up as an independent institution than to operate it as a branch of an existing bank.

Seidman said he is talking to states about the possibility of changing their laws on branching to increase the number of potential bidders.

In many farm areas, healthy banks already have more deposits than they can loan, so there is no incentive for them to buy the deposits of a failed bank.

Seidman said that regulators sometimes find it impossible to keep a deteriorating bank together long enough to find bidders. He said the tests that the FDIC must apply to determine what action is the least costly to the insurance fund sometimes require the agency to pay off depositors even when bidders can be found.

In other cases, the costs of acquiring a failed bank are not worth it to a healthy institution in a period of low interest rates, Seidman said.