After weeks of campaigning for his Manhattan congestion pricing scheme, Mayor Bloomberg could get a final answer today on whether the centerpiece of his ambitious environmental plan for New York City will go forward.

Mr. Bloomberg will be pushing the proposal in Albany today in the hope that lawmakers broker a last-minute agreement, which would allow the city to qualify for an estimated $500 million in federal transportation funds.

Governor Spitzer last night convened a last-minute negotiating session to try to finalize a deal that would involve an agreement on congestion pricing and campaign finance reform and other issues, a source said.

The U.S. Department of Transportation has said that if an agreement is not reached today, the city will no longer be eligible for the $500 million. Some Albany lawmakers have suggested that an 11th-hour compromise might allow the city to pursue the federal funds without final Albany approval for the mayor’s congestion pricing plan.

Even that idea appears to be out of reach, because the speaker of the Assembly, Sheldon Silver, who holds the final sway over the vote, does not plan to be in Albany today.

Yesterday, Mr. Bloomberg painted a dire picture of the crippling congestion that would ensue if his plan is shot down.

He said that if the city fails to secure the federal funding set to expire today, projects such as the Second Avenue subway line, a rail link between Lower Manhattan and John F. Kennedy International Airport, and an expansion of bus routes could be adversely affected.

“If we were to miss this opportunity, we are going to have mass transit on the front pages of our papers virtually every day for the foreseeable future,” Mr. Bloomberg said after stumping for the proposal at churches in Brooklyn, Queens, and Manhattan.

There will be pressure to raise subway and bus fares and to scale back transit projects, he said. He predicted the transit woes would lead to “people screaming that they can’t get to work” because of long commutes. He said at some point the city would find businesses are leaving and new ones staying away because of traffic congestion.

Mr. Bloomberg is scheduled to meet with Mr. Spitzer, Senator Bruno, and Senate Democrats today, while Mr. Silver is scheduled to meet with Democratic Assembly members at his Manhattan office, making a congestion pricing vote a nearly certain geographic impossibility.

Messrs. Spitzer and Bruno publicly support Mr. Bloomberg’s proposal to charge motorists $8 to drive into Manhattan below 86th Street on weekdays and $4 to drive within the Manhattan zone where drivers are charged, but Mr. Silver has been critical of the proposal.

An Assembly member of Brooklyn who supports congestion pricing, Karim Camara, said he would consider it a tragedy if the city lost the federal funding. He said congestion pricing is “on deathwatch,” but noted there’s a chance it may not die.

“Otherwise, I don’t see the speaker calling us to the city to have a conference on it,” he said. “As for what percentage of a chance, I really don’t know.”

On Friday, Mr. Bruno introduced a revised congestion pricing bill that the Senate is expected to vote on today. The bill would create a 12-member commission with equal representation by the Assembly, the Senate, the governor, and the mayor that would make recommendations about the program and how to spend money collected from the congestion pricing fees.

The dean of Baruch College’s school of public affairs, David Birdsell, said a congestion pricing failure for Mr. Bloomberg would be bad news for the mayor’s environmental plan because the congestion fee is its first major component.

“On the other hand, I think he can at least make the argument that this has less to do with congestion pricing and more to do with the poisonous atmosphere in Albany today,” he said.

Mr. Bloomberg’s patience for naysayers seemed to be wearing thin yesterday. When a reporter began a question by suggesting congestion pricing would fail, Mr. Bloomberg quickly cut him off.

At City Hall, supporters and opponents of the congestion plan held dueling news conferences in a last-ditch attempt to win over legislators.

Supporters of the plan brandished a letter from doctors and public health researchers calling congestion pricing “an essential part of the overall effort to improve health in New York.”

A City Council member of Queens, David Weprin, released a report concluding that congestion pricing would have negative health effects outside the congestion zone because commuters would drive to transit hubs there to travel into Manhattan.