Governor Spitzer is open to supporting Mayor Bloomberg’s congestion pricing proposal, a critical but contentious component of the city’s 2030 plan, but is withholding his support until he reaps more concessions from the city, sources close to the governor say.

Mr. Spitzer has yet to take a public position on the mayor’s plan to ease traffic and raise funding for major transit projects by imposing a fee on daytime motorists entering or leaving the southern half of Manhattan.

Sources said Mr. Spitzer is warming up to the road-use charges, known as congestion pricing, and is negotiating to ensure the state oversees the $31 billion in mass transit capital projects connected to the mayor’s plan.

Talks between the city and state have gone beyond the question of who would be pulling the purse strings of the transit plan. Spitzer administration sources say the governor is also looking to exchange his support for a larger say over major development projects in the city that are under way or waiting to be built.

A spokesman for Mr. Bloomberg declined to comment on discussions between the governor and the mayor concerning PlaNYC, the mayor’s long-term environmental and infrastructure blueprint for the city.

The mayor came to Albany two weeks ago to ask the governor for his support, as well as to pitch his plan to state lawmakers. Bloomberg officials are aiming to have the plan ratified before June 21, when the Legislature goes out of session. Mr. Spitzer said he had questions concerning several components of the plan, but generally gave the mayor a friendly reception.

While Mr. Spitzer’s support for congestion pricing would not guarantee its passage in the Legislature, it could increase the odds by providing political cover to lawmakers fearful of angering voters.

Under the mayor’s plan, drivers of cars would be charged $8 for driving into or out of Manhattan south of 86th Street — with the exception of FDR Drive, the West Side Highway, and West Street — on weekdays between 6 a.m. and 6 p.m. Trucks would be charged $21. The fees would offset any other tolls paid by motorists, so that a driver of a car wouldn’t have to pay more than $8 a day to enter Manhattan. The system would use technology similar to E-Z Pass.

Bloomberg officials are predicting that traffic would decrease within the charge zone by 6.3% and that speeds would increase by 7.2%.
The mayor’s plan is backed by a coalition of environmental and civic groups. It has also received the endorsement of the New York Times editorial board, whose opinion Mr. Spitzer is known to respect. The Times published an unsigned editorial last week urging the governor to sign on to congestion pricing.

Parking garage owners and non-Manhattan business groups are leading the charge against the mayor’s plan.

A Quinnipiac University poll released last week showed that while the overwhelming majority of New Yorkers think traffic is “a very serious problem,” 56% of city residents are against forcing motorists to pay a fee to drive into Manhattan. Most Manhattan residents, however, favor congestion pricing, according to the poll.

The mayor is proposing that the congestion pricing revenue stream would flow to a new transit financing authority, called the SMART authority, which would be jointly controlled by the city and state.

The authority would use the $380 million a year generated by the new fees (a number projected to increase to $900 million by 2030), as well as city and state contributions, to pay for an assortment of mass transit projects that would otherwise lack funding.

Sources close to the governor said he is opposed to establishing a new authority and would prefer that the multibillion-dollar pot of money be placed under the care of an existing state-controlled authority. They are confident that Mr. Bloomberg would be willing to accept such a concession.

Ultimately, the fate of congestion pricing rests in the hands of state lawmakers, many of whom say they are undecided.

The plan has stirred the most concern among many non-Manhattan and suburban lawmakers, particularly in the Assembly, who say congestion pricing is just a commuter tax with another name.

Senate Republicans, who have relied on Mr. Bloomberg for financial support, have responded more positively to congestion pricing.

Yesterday, the leader of the Senate Democratic minority, Malcolm Smith, who represents a district in Queens, announced that he was backing the mayor’s plan.

The move by Mr. Smith, who has closely aligned himself with the governor, was seen by some in Albany as a precursor to Mr. Spitzer’s eventual embrace of the plan.

“I would imagine that Malcolm is the beginning of the process,” a Republican senator of Brooklyn, Martin Golden, said. “I believe that many on the Democratic side as well as the Republican side will support it, and I believe that there is a good possibly that the governor will support it,” he said.

Opposition to congestion pricing runs deepest in the Democrat-controlled Assembly, whose leader, Speaker Sheldon Silver, has said he would withhold his judgment on congestion pricing until after the Assembly holds public hearings on the plan.

A split between the governor and the speaker on congestion pricing would be one of the few times they have disagreed on a major issue since the battle over choosing the state comptroller.