ALBANY — Mayor Bloomberg’s congestion pricing proposal missed a key federal deadline yesterday, but the speaker of the state Assembly, Sheldon Silver, offered a compromise that, while weak, could keep the plan on life support.

Mr. Silver, who has been critical of the plan to make drivers pay to travel in the busiest part of Manhattan, did not reconvene his members for the necessary vote in Albany but said he would support a bill that creates a commission to study the proposal.

Supporters of Mr. Bloomberg’s plan said, however, that the commission, which would not report back until March 2008, would never satisfy demands from federal transportation officials. They said the only compromise that could keep the plan alive would be a commitment by Mr. Silver to authorize the $8 driver fee but reserve the right to study how it would be implemented.

“What the feds need is a plan to be implemented. They don’t need a commission to study the ramifications of congestion pricing,” the Republican majority leader of the state Senate, Joseph Bruno, said. “They don’t need a commission for study and review. What they need is a plan.”

The U.S. Department of Transportation set yesterday as the deadline for approving congestion pricing and qualifying for more than $500 million in federal transportation funds. Over the last week, the agency has been saying it would likely refuse anything less than full approval of a pilot program. A spokesman for the department did not return numerous calls last night.

Mr. Silver, who controls the final state vote, said yesterday that he planned to work into the night to hammer out a “letter of statement” that he, Governor Spitzer, and Mr. Bruno would send to the federal government.

“That’s still a subject to be worked out with the mayor tonight,” he told reporters in Lower Manhattan.

But Mr. Bruno said the speaker’s current proposal “wouldn’t work,” and Mr. Bloomberg’s office was silent last night on whether it was getting any closer to a deal.

The mayor has billed the fee — which would charge drivers below 86th Street — as crucial to both the environment and the economy. He has said part of the $500 million would go toward mass transit upgrades, helping to get people out of their cars.

But many elected officials outside Manhattan see it as a regressive tax that would exempt the wealthy while financially burdening their middle-class constituents.

Mr. Bloomberg spent much of yesterday in Albany but left after a fruitless attempt to beat the clock and win over lawmakers.

Some state lawmakers said the mayor, who just a few months ago called congestion pricing a “political nonstarter,” did not do an effective job of selling it in the state capital. The mere fact that he was in Albany on the day of the deadline, pitching it to a group that were presumed to be locked up, had people scratching their heads. Additionally, many state politicians never bought into the idea that there was a hard-and-fast deadline.

Assemblyman Richard Brodsky, a vocal opponent of the mayor’s plan, called the congestion proposal “Jets Stadium redux,” referring to Mr. Bloomberg’s failed attempt to get state approval for an Olympic football stadium on Manhattan’s West Side. He said state lawmakers are “not going to get rolled over by a phony threat.”

Several of the Democratic senators Mr. Bloomberg met with yesterday morning expressed disappointment that the mayor has said publicly that he plans to back the Republican majority despite his declaration that is no longer a member of the party. Others said the mayor was simply dismissive of questions about the plan, including how parking around the zone would work and whether exemptions could be created for the disabled.

“I think there was a golden opportunity to really do something remarkable. But there seems to have been an air of you’ve got to do this because — almost a holier than now attitude,” state Senator Bill Perkins, a Democrat of Harlem, said.

Mr. Silver said his commission would include representatives from the Senate, Assembly, mayor, governor, and City Council. He also said he wanted the council, whose members have until now not needed to take a public position on the plan, to pass a “home rule” resolution asking Albany to act.

That could give the members of Mr. Silver’s conference political cover from council members looking to challenge them when they are termed out of office and using congestion pricing as a sticking point.

“I think some of my colleagues are concerned about voting for something and then discovering that their local council member is attacking them for it,” Assemblyman Richard Gottfried said.

The president of the Campaign for New York’s Future, Michael O’Loughlin, urged Mr. Silver to go further in his commitment and to act fast.

“Federal guidelines are very clear: They require a plan that implements congestion pricing, and not one that simply studies it,” he said. “The best way to study congestion pricing is to implement the pilot program.”