United Savings Bank, which operates 15 branches in Northern Virginia, is on the verge of collapse following a nearly $10 million loss in the second quarter that has left the savings and loan just barely solvent and has completely wiped out its capital, the cash cushion that protects the federal deposit insurance fund against losses.

The thrift, once the 15th-largest S&L in the state, has suffered a series of recent blows to its bottom line because of problems in its commercial real estate portfolio.

Its failure would make United the first casualty among financial institutions of the slowdown in the Washington area commercial real estate market.

A takeover of United by federal regulators also would mark the first time government officials have had to intervene in a local thrift's operation since the Maryland savings and loan crisis of 1985, when dozens in Maryland went under.

United President Stanley Burns said in a statement, "United needs an immediate infusion of capital ... but no definite source of new capital is foreseeable in the near future. United is working closely with state and federal regulators to structure an appropriate solution for the bank."

Burns assured depositors that "in any situation ... depositor funds up to $100,000 will continue to be insured by the FDIC."

Disclosure of the thrift's problems comes just one month after Citibank Federal Savings Bank, Citicorp's wholly owned District thrift, announced that it had broken off merger talks with United Savings, which now has $421 million in assets.

Although Citibank officials declined to comment on the breakdown of the talks, sources said yesterday that Citicorp officials walked away after they found out about the depth of United's problems.

Burns, who has been president of the S&L for little more than a year, has said that United's problems are rooted in a long history of mismanagement that culminated in the resignation of the thrift's top executives last summer, after an investigation by the Securities and Exchange Commission into possible insider trading in United's stock.

Although the thrift has spent the past year trying to puts its financial house in order with a new management team, a new business plan and an overall cleansing of its troubled loan portfolio, the thrift said yesterday, "these efforts have recently been overtaken by the depressed local real estate market."

United's quarterly loss was primarily the result of a $6.1 million addition to its loan-loss reserve, the cash cushion that protects against possible loan defaults.

United has seen its portfolio of troubled real estate loans increase dramatically over the first two quarters of 1990 as the Northern Virginia commercial real estate market weakened. Nonperforming loans, those that are no longer paying interest, now total $55.6 million.

The thrift made a number of loans in Herndon and in the Dulles corridor, two areas hit hardest by the real estate slowdown.

It also lent millions of dollars to McLean developer Mohammed Hadid, who has recently been negotiating with creditors to restructure parts of his billion-dollar empire. United has been working with Hadid on a $20.5 million loan for a Tysons Corner office building that the developer has defaulted on; it is unclear where those negotiations stand.

United said yesterday that its problems have left it just barely solvent, with assets of $421.7 million and liabilities of $421 million.

And it said its capital has dipped below zero.

United said that overall, it lost $11.5 million in the first half of 1990, compared with a loss of $3.6 million in the same period last year.

Burns said yesterday that despite management's efforts, "the depressed local real estate market has had a critical impact on United because of United's earlier real estate loan concentrations."

He said he does not expect the Office of Thrift Supervision, the federal agency overseeing the industry, to approve United's capital plan, which was submitted seven months ago to show regulators how the thrift would get back on its feet.