ALBANY – The executive director of the MTA said yesterday she will depend increasingly on private sources of cash to expand and maintain an aging fleet of buses, subway cars, and trains.

In testimony before the joint Legislative Fiscal Committee, the Metropolitan Transportation Authority official, Katherine Lapp, said that a new subway line along the East Side of Manhattan probably will not be built without private support and that cash from the proposed sale of air rights over MTA yards on the West Side would be spent on essential items in the agency’s five-year capital plan.

Ms. Lapp’s testimony came one week after Governor Pataki proposed committing $2.5 billion less than the $17.2 billion the MTA requested for “core” operations through 2009, and it came two days after a devastating subway control room fire in Manhattan that transit officials said could take years to fix.

Ms. Lapp said she did not know whether the authority is insured against damage from the fire. If it isn’t, then costly repairs could cut even deeper into an operating budget that Ms. Lapp described as already under serious strain.

“This $14.7 billion is a good start,” Ms. Lapp said. But she continued: “The reduction from our proposal will require the MTA board to make difficult choices as to how to allocate our resources. We will do everything in our power to keep the basic infrastructure of our system in good operating condition.”

Already off the table, Ms. Lapp said, are plans to increase purchasing of new subway cars, buses, and trains. A number of planned station rehabilitation projects will also have to wait, she said.

Ms. Lapp stressed that the safety of the transportation system, which handles 8 million passenger trips each weekday, would not be compromised. But reliability, she said, would definitely take a hit.

A Westchester Democrat who has called for a constitutional amendment that would limit the governor’s budgetary power, Assemblyman Richard Brodsky, said: “The governor’s proposal will yield a system of declining service and increased fares. This is no way to run a transportation system.”

But it is not clear how the state Legislature could help Ms. Lapp and the MTA secure additional funds. A December court decision requires lawmakers in the state Assembly, which is controlled by Democrats, and the Senate, which is controlled by Republicans, either to accept or reject the governor’s budget as is, rather than pass a version that legislators have modified. And since similar votes from the split houses are unlikely, changes will have to come in the form of amendments introduced separately from the budget itself – after appropriation bills in areas such as transportation have already been decided by an up or down vote.

Mr. Brodsky told Ms. Lapp that she would have to criticize the proposed MTA appropriations if she expects to enlist the help of legislators. He said the governor would consider raising his commitment only if Ms. Lapp and her boss, MTA Chairman Peter Kalikow, publicly oppose Mr. Pataki’s plan.

“The choices you are giving us, on the Rodney King theory that we can all get along, are not going to be good enough,” Mr. Brodsky said. “If the MTA wants us to turn down the governor’s capital plan and his funding packages, then you’re going to have to tell us that. If you think we are prepared to go against Governor Pataki without Katherine Lapp and Peter Kalikow standing by us, you’re wrong.”

Ms. Lapp did not take the bait. Under harsh and extensive questioning from Mr. Brodsky, she said the authority would “find ways to chip away” at its expenses – including an anticipated $586 million deficit next year – and would do nothing to compromise the system’s safety. At no point did she directly say the governor or his budget was putting the system in a bind.

Instead, Ms. Lapp outlined private alternatives to finance new construction projects and supplement operational costs in coming years. She said such private assistance on a proposed new line along Second Avenue could result in different fares schedules for commuters on that side of town. When Mr. Brodsky pressed her on whether she thought that was a good idea, Ms. Lapp said, “As a person that uses the subway system, I personally am not necessarily enamored with the idea, but I’d have an open mind.”

The MTA plans to pay for its $17.2 billion budget for core operations with a mix of federal funds, state funds, bonds, investment income, and the sale of assets. An additional $500 million would be required over the next five years, the MTA board estimates, for security.

The authority balanced its 2005 budget with a fare increase and a variety of austerity measures. But closing the anticipated budget gap next year, Ms. Lapp said, would require the sale of several MTA assets. That means the MTA is counting on the sale of the air space for the New York Sports & Convention Center, a major element of Mayor Bloomberg’s plan for revitalizing the West Side. Last week, the MTA said it had engaged an appraiser to determine a fair price for the yards. Ms. Lapp said she had been advised by an MTA attorney to keep the appraisal amount to herself.