Maryland Gov. Larry Hogan (R) agreed Tuesday to delay a key vote on his plan to add toll lanes to the Capital Beltway and Interstate 270 after the state’s comptroller said he and the public needed more time to review “important revisions” to the proposal.

Comptroller Peter Franchot (D) had asked Hogan on Monday to delay Wednesday’s vote by the Board of Public Works. Franchot said he was concerned that changes proposed by the Maryland Department of Transportation “would substantially broaden and accelerate” the plan that he had agreed to in June.

Hogan spokesman Michael Ricci said the governor agreed to delay the vote until Dec. 18 “as a courtesy to the comptroller.” He declined to elaborate.

Under state law, the three-member panel, composed of the governor, comptroller and state treasurer, must approve any changes to the plan because MDOT is pursuing it as a public-private partnership. With an estimated value of more than $9 billion, it would be the biggest such arrangement in the country.

Among the changes, MDOT is seeking permission to begin buying private property along the highways as it comes up for sale, rather than waiting until a federally required environmental impact study is completed and a contract approved. MDOT also plans to solicit private-sector proposals for the Beltway and I-270 simultaneously, rather than pursuing I-270 first, as the board approved in June. State officials said doing so would allow work to begin at the American Legion Bridge, on which the governors of Maryland and Virginia recently agreed to share the cost of rebuilding and expanding.

Highway expansion opponents have focused their lobbying efforts on Franchot because he is considered the board’s swing vote. Treasurer Nancy K. Kopp (D), who represents the General Assembly on the panel, has previously opposed the project, saying she is concerned about its potential environmental impact.

Franchot, who is strongly considering a run for governor in 2022, asked that the vote be delayed to allow for more public vetting.

The reluctance of Hogan’s office to confirm the vote delay until late Tuesday spurred speculation that his and Franchot’s offices had spent the day trying to negotiate an agreement. However, Len Foxwell, Franchot’s chief of staff, said no discussions had occurred Tuesday.

Foxwell said Franchot believed the Hogan administration was trying to rush the vote after the short Thanksgiving holiday week. He said the comptroller is particularly concerned that the state now wants to begin buying private property along the highways as it becomes available. Franchot supported the plan in June on the condition that no property be acquired until an environmental impact study is complete, Foxwell said.

Soliciting proposals simultaneously for the Beltway and I-270, all the way to Frederick, would speed up the project, Foxwell said. It also could result in the state pursuing a contract for upper I-270 before that environmental study is complete, he said.

Franchot also is concerned that the state is backing off its commitment to spend 10 percent of its share of net toll revenue on public transportation in Montgomery and Prince George’s counties, Foxwell said.

“Commitments made to the comptroller in exchange for his support in June now appear to be very much in question,” Foxwell said. “These are dramatic ­changes to what is already the largest [public-private partnership] project in North American history. The magnitude of these changes . . . demands that we take a much more careful look at the proposal.”

Under MDOT’s proposed public-private partnership, teams of companies would build the lanes and finance their construction in exchange for keeping most of the toll revenue over 50 years. No taxpayer money would be spent, state officials have said.

Tolls would adjust with traffic to keep the lanes flowing at a minimum 45 mph. The regular lanes would be rebuilt but would remain free, state officials have said.

In documents submitted to the Board of Public Works, MDOT said the solicitation process would be “competitive and transparent.” The latest approach, the agency said, would ensure “sufficient market participation,” better pricing for the lanes’ design and construction, and “more collaborative dialogue” among the companies, the state and local communities.

Critics say the changes would rush the process, give short shrift to environmental and community concerns, and not allow enough public scrutiny of contracts worth billions.

In a letter Monday, 84 members of the General Assembly asked the Board of Public Works to delay the vote, saying the public needed more time to review MDOT’s new plan.

“MDOT is well aware of the controversial nature of the project and the wide array of concerns that have been expressed,” the letter said. The lawmakers cited concerns about the structure and cost of a public-private partnership, local agencies being denied “crucial information” to evaluate the proposal, and divided public opinion.

“A multi-billion dollar, multi-decade public-private partnership requires more than a few days of review over a holiday week,” the letter said.

Hogan has said the toll lanes are necessary to relieve traffic congestion that will otherwise stifle the state’s economy and continue to create misery for motorists as it grows worse.

Ricci, Hogan’s spokesman, said the vote’s scheduling wasn’t rushed. He said Franchot and Kopp received information about the proposal Nov. 22, allowing the standard amount of time for review before a meeting. State transportation officials briefed Board of Public Works staff on Nov. 27, he said.

Franchot, he said, “abruptly canceled” another briefing scheduled for Monday afternoon.

Critics of the toll lane plan, including transit advocates, say the state needs to slow down.

Stewart Schwartz, executive director of the Coalition for Smarter Growth, said the state shouldn’t be pursuing contracts before it has thoroughly evaluated a range of traffic-relief options. Those include encouraging more development at Metro and MARC commuter rail stations, expanding public transit and providing financial incentives for motorists to use transit, he said.

Schwartz said he has been surprised by how little public airing Hogan’s toll lanes proposal has received. When the Board of Public Works approved the plan in June, he said, “I was shocked by the lack of in-depth evaluation of alternatives, the risks, the finances and other issues.”