WASHINGTON --- The agency that guarantees bank deposits said Thursday that there are no immediate plans to borrow money from the government to bolster its insurance fund, which has shrunk under the weight of collapsing banks.

The fund fell 20 percent to $10.4 billion in the second quarter as U.S. banks lost $3.7 billion, the Federal Deposit Insurance Corp. said. That's the fund's lowest point since 1992 at the height of the savings-and-loan crisis.

The FDIC estimates bank failures will cost the fund around $70 billion through 2013. Eighty-one banks have failed this year, and more are expected to fall because of souring loans for commercial real estate.

That threatens to deplete the FDIC's fund. It has now slipped to 0.22 percent of insured deposits, below a congressionally mandated minimum of 1.15 percent. The $10.4 billion in the fund is down from $13 billion at the end of March and $45.2 billion in the second quarter of 2008.

Asked about a possibility of tapping the U.S. Treasury, FDIC Chairman Sheila Bair said: "Not at this point in time. I never say 'never,' but not at this point in time, no."

She reaffirmed the likelihood of an additional fee on U.S. banks this year to help replenish the fund, atop the estimated $5.6 billion from a new emergency premium that took effect June 30.

Despite the shrinking insurance fund, customers have nothing to worry about. The FDIC is fully backed by the government, which means depositors' money is guaranteed up to $250,000 per account. And the agency still has billions in loss reserves apart from the insurance fund.

Still, the FDIC needs to replenish its fund. It can do so by charging banks higher fees or by taking the more radical step of borrowing from the Treasury, where its credit line reaches $500 billion.