The Resolution Trust Corp., the agency disposing of failed savings and loan institutions, could need about $100 billion to cover losses and provide working capital in the fiscal year that starts Oct. 1, RTC Chairman L. William Seidman told a congressional committee yesterday.

Members of the House Banking, Finance and Urban Affairs Committee chafed at the prospect of appropriating that much money and warned that it would be difficult to vote more funds for the savings and loan cleanup. Members complained that the Bush administration was asking for a "blank check" and was treating the Treasury as a "bottomless pit." Two representatives demanded to know where the "light at the end of the tunnel" was.

But Treasury Undersecretary Robert R. Glauber told them that because of federal deposit insurance, "We are committed to make these payments. We have no choice." He said the blank check was written when Congress and an earlier administration insured deposits at thrifts. "Now it's a question of making good on it," he said.

Meanwhile, White House deputy press secretary Stephen T. Hart brushed off a resolution by the National Governors Association calling for the president and Congress to set up an independent panel to study the savings and loan mess.

"We do feel it is unnecessary to create another bureaucratic body," Hart said.

RTC spending falls into two broad categories: so-called working capital that the government says it needs to manage properties and run thrifts until they can be sold; and losses, such as money paid to cover deposits, that won't be covered by asset sales.

The figures cited by Seidman were at the high end of the range for losses given earlier by Treasury officials and somewhat higher than Treasury's earlier estimates for working capital. Just two weeks ago, the Office of Management and Budget estimated in its mid-session review that the RTC would require a total of $63 billion in the next fiscal year.

But Glauber said the higher figures showed that the RTC was making faster progress and did not mean that Treasury's best estimate of the final losses it expects from the cleanup had changed from the $132 billion Treasury Secretary Nicholas F. Brady had indicated in testimony last month.

Glauber did not make an appropriation request on behalf of the administration, but instead laid out three alternatives for the committee: a stopgap $5 billion to $10 billion appropriation that would tide over the RTC until the beginning of the 1991 calendar year; an appropriation of funding required for the entire fiscal year; or the passage of "permanent, indefinite authority to complete the job."

Committee Chairman Henry B. Gonzalez (D-Tex.) pressed Glauber to say what Treasury's preference would be, but Glauber left that to the committee.

"Congress can give us whatever they choose. If they give us less, we'll be back sooner. We've got to do this as cheaply as possible, but we've got to do it," Glauber said.

"I don't think that's a sufficient answer," snapped Rep. Toby Roth (R-Wis.), who predicted that Congress would reject a request for more money.

Glauber warned that "we cannot afford to let the RTC run out of money and we must not let the process grind to a halt."

In breaking down the RTC needs, Seidman estimated in his written testimony that the RTC would need "a minimum of another $50 billion" in the 1991 fiscal year to cover losses on the insolvent thrifts seized by the government. In oral testimony, he said the figure could be only $30 billion to $40 billion.

He said that the RTC would need another $50 billion to $60 billion for working capital during the same year.

The Treasury's most recent estimates have been that the RTC would use between $20 billion and $40 billion for working capital and to have losses of $30 billion to $50 billion.

Seidman also indicated that the RTC would use working capital borrowings of $60.6 billion in the current July to September quarter alone, $34 billion in new money.

The high level of borrowing prompted Treasury securities analysts to expect "record amounts" of Treasury borrowing for the next several quarters.

Glauber asserted that future RTC working capital would be raised through the Treasury instead of by issuing separate bonds through the Resolution Finance Corp.