Virginia Gov. Bob McDonnell speaks to the press in front of a statue of George Washington at the Capitol on Feb. 5 in Richmond. (Steve Helber/AP)

The Virginia House of Delegates on Friday approved a landmark transportation plan backed by Gov. Robert F. McDonnell, but the proposal stalled in the Senate, where Democrats insisted on guarantees for a Medicaid expansion plan.

The Senate adjourned without a vote as Democrats threatened to derail the transportation deal, which trims gas taxes but raises the sales tax and some fees to deliver about $880 million a year for roads, rail and mass transit.

Senate Democrats insisted on a link between the transportation plan and Medicaid expansion, exacting a promise from McDonnell (R) that he would not undercut a deal meant to expand the federal health program for the poor. The Senate was waiting for McDonnell to put that in writing when it adjourned.

On Saturday, the last day of the scheduled legislative session, the Senate is expected to vote on the transportation funding plan. If it passes, it would become the state’s first comprehensive road and rail plan in a generation.

In a statement Friday evening, the governor commended the Senate’s progress on Medicaid. But he also said he reserved the right to review what House and Senate conferees come up with on an expansion plan when the budget is adopted.

A spokesman for McDonnell said Medicaid expansion and transportation remain separate issues. Still, several senators said the governor had agreed Thursday night to go along with the Medicaid compromise to pave the way for the transportation bill.

Throughout the session, Democrats have demanded that Virginia move to quickly expand Medicaid as part of the federal Affordable Care Act. But Republicans, more wary of the program, have said the state should first wring reforms from Washington before expanding the program.

On the eve of Friday’s vote, some Democrats in the House had also threatened to condition their support for the transportation bill on Medicaid expansion, but the subject seemed to vanish as the House debate began. The House vote was 60 to 40, with Republicans and Democrats joining ranks to pass it.

“We have a choice today. We can do something, or we can do nothing,” said Del. David B. Albo (R-Fairfax).

At its center, the transportation measure would substantially cut the fuels tax but raise the sales tax from 5 percent to 5.3 percent and allocate a portion of existing revenue to roads. It would also raise funds for regional authorities in Northern Virginia and Hampton Roads and empower them to spend the money only on transportation in those areas.

The plan also would loosen the tie between fuel consumption and tax revenue to pay for roads, and it would provide more money from sales taxes — which also fund schools, law enforcement and other services — toward roads.

The compromise forced Republicans to agree to higher taxes while requiring Democrats to change their opposition to diverting additional funds raised by sales taxes, known as the general fund, to roads.

Del. S. Chris Jones (R-Suffolk), a chief architect of the compromise, thanked the governor for starting the process, and he thanked several Democrats, including Del. Vivian E. Watts of Fairfax, a former transportation secretary, for working out the nitty-gritty details. Jones urged members to vote for the bill, saying that any pact forces people on each side of a conflict to accept something they might not like but that both sides need.

“I will represent that this bill before us is something that we really need,” he said.

The transportation package approved by the House was markedly different from the initiative initially pushed by McDonnell and sponsored by House Speaker William J. Howell (R-Stafford). But supporters credited the governor with setting the bill in motion and Howell for removing a key hurdle when he killed a surprise redistricting plan that Senate Republicans shoved through the evenly divided chamber when a Democratic senator was out of town.

“If the governor didn’t put his reputation on the line and make this a legacy issue, we wouldn’t have gotten to the point where we are today,” said Del. Mark Keam (D-Fairfax) after the vote. “He stuck his neck out.”

But Keam said that although McDonnell may get to boast of a political breakthrough, Democrats and Northern Virginians get more. “The governor gets a bumper sticker out of this, but we get a good, solid, substantive bill out of this, meaning Democrats,” Keam said.

The plan would cut the gas tax by about a third, but it would be tied to inflation and rise over time. The proposal replaces the current 17.5 cents-per-gallon levy with a new 3.5 percent wholesale gas tax. The tax on diesel would remain about the same, but it would be converted from a flat per-gallon tax to a 6 percent wholesale tax and also rise with inflation. The bill would also double the registration fee on hybrid vehicles to $100, reflecting the governor’s view that vehicles of all types should contribute to the cost of the road network.

It also gives money to the Northern Virginia Transportation Authority, an entity that has existed mostly on paper since the legislature created it in 2002.

The bill would raise the sales tax in Northern Virginia and Hampton Roads by 0.7 percentage points so that, combined with the higher statewide sales tax, those areas would pay 6 percent on nonfood items.

The authorities would be required to spend the money based on a formula that ranked the efficacy of improvements most likely to ease congestion — a key element pushed by Del. James M. LeMunyon (R-Fairfax).

“I wouldn’t have voted for the bill without that,” LeMunyon said.

Mark Ingrao, president and chief executive of the Greater Reston Chamber of Commerce, said his group went into the process believing that “everything was on the table” regarding possible solutions for the region’s transportation problems. He was particularly pleased by the prospect of “allowing the counties to tax themselves. In Northern Virginia that’s an excellent thing, because then the money that’s raised stays right here,” Ingrao said.

But a majority in the Republican caucus rejected the deal, which they said would force Virginians to dig more deeply into their pockets. Thirty-five Republicans voted against the deal, including one independent who caucuses with the GOP.

“It morphed from the original plan. I respect everybody’s decision, but this is a tax increase that I couldn’t stomach,” said Del. Timothy Hugo (R-Fairfax). Only one Democrat from Northern Virginia — Del. Scott A. Surovell (Fairfax) — voted against the deal, although many had reservations, especially because of the greater diversion of general funds for roads.

House Minority Leader David J. Toscano (D-Charlottesville), who urged passage of the deal, said the vote was perhaps the most important he has cast.

“This is no longer the governor’s bill. This is no longer the speaker’s bill — with all due respect, ” he said. “It is now our bill, and it rises and falls with us, here and now, today.”

Toscano acknowledged that he, too, was troubled by using more general funds to build roads.

“There are things I don’t like about this package,” he said. “But I’m willing to support it because although I don’t think it solves every problem, it solves a lot of problems. It’s not a solution for a generation, but it’s a step forward.”

Ben Pershing contributed to this report.