Gov. Bob McDonnell’s administration said 40 transportation projects across the state would be gutted if the legislature included another $300 million in bonding for the extension of Metrorail to Dulles International Airport.

This 2010 file photo shows a westward facing view of Dulles Toll Road from the Wiehle Ave. overpass where the Silver Line of the Metro is being extended to Dulles Airport, in Reston, VA. (Jahi Chikwendiu/The Washington Post)

Most House and Senate budget negotiators agreed last week to the two-year, $85 billion spending plan, paving the way for a Tuesday vote by all 140 members of the General Assembly.

But Republicans in the Senate need at least one Democrat to vote for the budget to pass the evenly divided chamber. Lt. Gov. Bill Bolling (R) breaks tie votes, but not on the budget. Sen. Charles Colgan (D-Prince William) said he is considering voting for the budget.

Democrats secured several of their priorities but failed to get House negotiators to provide an additional $300 million for Dulles rail after McDonnell’s administration said it would not spend more than $150 million.

The Senate budget had included bonds to help hold down tolls in Northern Virginia, which are due to be increased to pay for the second phase of Metro’s new Silver Line. That decision could jeopardize the project, according to some, though a more broadly held view is that it will still move forward but result in heavy toll increases.

The first phase of the $6 billion Silver Line is under construction from Falls Church to Reston and is expected to open in late 2013 or early 2014. Construction on the second part of the project, which will run to Dulles and into Loudoun, is expected to start in January and be completed in five years.

To help pay for the project, a one-way trip that now costs $2.25 could increase to $4.50 as early as next year. By 2018, tolls for that one-way trip could rise to $6.75.

Senate Democrats on Thursday began a petition to ask supporters to “tell Governor McDonnell that the sky-high tolls in his budget are unacceptable.”

“Governor Bob McDonnell’s band-aid transportation gimmicks are taking Virginia backwards,’’ Sens. Richard Saslaw (D-Fairfax) and Don McEachin (D-Henrico) said in an e-mail. “By signing this petition, you'll send Governor McDonnell the message that he must put money into Virginia's budget for these projects to reduce the amount families and businesses will have to pay in tolls.’’

McDonnell spokesman Tucker Martin said the senators’ ultimately goal — is the same one it always is — to raise taxes for transportation. “Both Senators are trying to use the state budget as just another opportunity to try to force their long desired gas tax hike,’’ he said. “Unfortunately, their posturing this time around could threaten funding for teachers and sheriffs, as well as road projects all across the state. That’s unacceptable. We aren’t going to let Virginians sit in traffic or not get their paychecks because Democratic senators demand a massive statewide tax increase.”