A day after Gov. George E. Pataki proposed a $105.5 billion budget for the next fiscal year, transit officials and others were digesting the transportation portion.

Though Mr. Pataki proposed increasing taxes and fees to pay for what he called $19.2 billion in transit spending over five years, transit advocates asserted yesterday that the source of most of that money was unexplained or based on unrealistic assumptions.

Of the total amount, $15.2 billion is intended for maintenance and upkeep and $2 billion for expansion. The figure also includes $2 billion in city funds for the westward extension of the No. 7 line.

The authority in September had requested $27.7 billion, including $17.2 billion for essential maintenance. Critics said yesterday that Mr. Pataki had not demonstrated where most of his proposed $19.2 billion would come from.

"It's the first time there's been such great uncertainty in 20 years," said Richard Ravitch, who was chairman of the authority from 1979 to 1983.

Mr. Ravitch said that some of his worst fears were being realized. "I have said since 1980 that the M.T.A. needs a recurring, inflation-sensitive source of revenue to fund a continuation of its capital improvement plan," he said. "This proposal does not appear to meet that test."

The governor's aides disputed that assertion, saying the governor planned to aggressively lobby Washington for greater transit aid and insisting that the authority had to exert greater discipline and find creative ways to pay for its needs.

"We're confident that working together with the M.T.A., we'll be able to achieve this plan," said Adam L. Barsky, a deputy secretary.

Ronald Rock, the deputy director of the state's Division of the Budget, said: "It's going to be a challenge for the M.T.A. They're going to have to do some hard actions, but they agree they'll be able to accomplish them."

Officials briefed on the plans yesterday said the authority might be asked to raise money by issuing pension-obligation bonds and by tapping into a $200 million stabilization account created late last year.

In addition, the officials said, Mr. Pataki supports an initiative proposed by the authority in 2002 to consolidate several subsidiaries. The Long Island Rail Road and the Metro-North Railroad would be combined into an entity called M.T.A. Railroads, but that plan has stalled in the Legislature.

Officials at the authority declined to comment on the governor's budget. "We're still reviewing it," said a spokesman, Tom Kelly.

Critics of Mr. Pataki said the measures would be minuscule compared with the shortfall in the authority's capital budget.

"I don't think anyone's quite absorbed the level of calamity that's likely to befall subway, bus and commuter rail riders," said Richard L. Brodsky, a Westchester County Democrat who is chairman of the Assembly committee that oversees the authority. Mr. Brodsky added, "Dramatic fare increases and worse service are inevitable." Mr. Ravitch and other transit advocates said they feared a similar outcome.

The authority raised tolls and fares last month, and it plans to do so again in 2006. But as a greater proportion of the budget goes to pay off old debt, the authority's capacity to borrow money against capital projects has declined.

Even normally circumspect business leaders expressed reservations about the plan, saying that the figures did not add up to the sum that the governor had promised.

Richard T. Anderson, president of the New York Building Congress, which represents construction, engineering, real estate and architectural firms in New York City, went further. "The budget proposal is enormously less than what the transportation needs of New York State require," he said.