The Metropolitan Transportation Authority, which is attempting to build support for another subway and bus fare hike, is warning in a new report that Mayor Bloomberg’s congestion pricing proposal would cost the agency hundreds of millions of dollars more than the city has estimated.

In a report detailing how a road tax would affect mass transit, the MTA outlined short-term service upgrades it would implement by next fall to prepare for the influx of riders who would be expected to leave their cars at home if congestion pricing were approved to begin in spring 2009. The report was released Friday to members of a commission studying congestion pricing.

The MTA report identifies $388 million of unfunded capital and operating costs associated with the service upgrades, and will likely add fuel to the debate on whether charging drivers to enter Manhattan south of 86th Street is the most practical way to reduce the traffic jams that are crippling the metropolitan region.

“There’s no explanation of where they’re going to get that money,” Assemblyman Richard Brodsky, a Democrat of Westchester, said of the unfunded costs. The congestion pricing plan “is in complete disarray. We’re at a point now where the transition from concept to plan has not been made.” Mr. Brodsky, who has been a vocal opponent of congestion pricing, pointed to air quality in neighborhoods around the zone that would be charged, and a subway and bus fare hike as issues that were notably absent from the report.

Both supporters and opponents of congestion pricing said the MTA’s report, which includes plans to ramp up subway and bus service by next fall, leaves out dozens of requests from city and state lawmakers for improvements such as subsidized commuter ferries for the south shore of Staten Island and the Rockaways, extra stops on Metro-North and Long Island Rail Road in the Bronx, Brooklyn, and Queens, as well as additional express bus and subway service. An MTA spokesman did not respond to calls yesterday.

The report recommends adding service on the no. 1 line. It also calls for increasing C line trains to 10 cars from eight, adding or widening subway stairways at many stations, and implementing one rapid bus lane in each borough within two years.

Mayor Bloomberg last spring unveiled a plan to charge drivers $8 to enter Manhattan south of 86th Street during peak hours, and charge trucks $21 to enter the city. In August, a 17-member congestion pricing commission was appointed to consider Mr. Bloomberg’s congestion pricing proposal, as well as alternatives that could also decrease traffic in Midtown Manhattan by 6.3%. In order to receive $354 million in federal funds to implement a road tax, the commission must hand over a recommendation for City Council and the state Legislature approval by March.

Mr. Brodsky, who was appointed to serve on the commission by the speaker of the Assembly, Sheldon Silver, said the MTA’s report, as well as a report on congestion pricing issued on Friday by the state Department of Transportation, were both incomplete. “They picked and chose what they were doing going to talk about and I can’t tell why,” Mr. Brodsky said. “They didn’t deal with an enormous range of issues that the commission’s going to have to resolve.” He said between 35% and 55% of trips in the charged zone are taxis, which would not have to pay the fee.

The DOT’s report also identified $166 million of capital costs that would be needed to support congestion pricing.

Supporters of Mr. Bloomberg’s pricing scheme said they were pleased that the report released by the state Department of Transportation confirmed that the mayor’s congestion pricing proposal is a significant method of reducing traffic delays throughout the metropolitan region, and seemed to favor it over an alternative traffic-calming proposal.

“The professionals in the State DOT have confirmed the assertions in the Mayor’s plan that a congestion pricing zone in Manhattan’s central business districts will result in reduced traffic congestion, cleaner air, and improve economic conditions in the 28-country metropolitan region,” the president and CEO of the Partnership for New York City, Kathryn Wylde, said via e-mail. Ms. Wylde is one of Mr. Bloomberg’s three appointees to the congestion pricing committee.

The state DOT also recommends creating leeway to tweak the pricing program after it is implemented because “there is not the level of detailed information available to accurately predict changing traffic patterns.”

After the costs to implement the system are funded, congestion pricing is expected to bring in about $390 million a year to the city’s coffers, according to city estimates.