The Virginia budget is more than a month late, and its fate is not quite certain.

When the General Assembly returns to the Capitol on Tuesday, lawmakers are scheduled to vote on a third version of the state’s two-year, $85 billion budget as state and local agencies brace for the impact of a potentially delayed spending plan.

The Virginia Department of Transportation has notified contractors that they should plan to halt work by May 1 because of the budget impasse in Richmond. A suspension would affect 473 construction and maintenance projects valued at $2.7 billion across the state, including bridges and interstate, primary, urban and secondary roads.

VDOT officials said Friday they are required to give contractors a two-month warning to wind down operations so they will have time to stop work and get paid. It takes weeks to shut down massive projects because they involve materials, heavy equipment, crews and work zones.

Also, school budgets must be adopted May 1, and county budgets by June 30. The deadline to inform teachers whether they will return to work next school year is Sunday, but most school districts have made decisions based on estimated budgets.

Robley Jones, director of government relations for the Virginia Education Association, said contracts allow district officials to terminate teachers if money is unavailable.

The General Assembly has been unable to agree on a budget that in essence helps pay for everything from prisons, road maintenance and colleges on the state level to courts, registrars and health care locally. Failure to adopt a spending plan by July 1 — the start of the state’s fiscal year — could lead to a government shutdown.

After failing to adopt a plan during the regular session that ended last month, legislative leaders appointed budget negotiators, who have agreed to a budget blueprint. Their agreement paves the way for a vote Tuesday, the day before the General Assembly is scheduled to consider Republican Gov. Robert F. McDonnell’s vetoes and amendments to non-budget bills.

Senate Republicans need at least one Democratic vote in the evenly divided chamber to approve the budget. Lt. Gov. Bill Bolling (R) can break tie votes but not on the budget. Democrats had balked at previous budgets because they sought more transportation funding, among other demands.

“I can’t imagine the Senate voting against it — all the good things it does for K through 12, higher education, safety net, for health and human and services, all across the board,’’ House Speaker William J. Howell (R-Stafford) said.

Sen. Charles J. Colgan (D-Prince William) has said he is considering voting for the budget, even though it does not include a Democratic priority — an additional $300 million for Metrorail to Dulles International Airport. Tolls would increase to pay for the second phase of Metro’s new Silver Line.

McDonnell’s administration said 40 transportation projects would have to be gutted if the state added the money Democrats sought, including three in Northern Virginia — Route 1 widening in Prince William County, and the interchange at Route 659 and the Battlefield Parkway extension in Loudoun County.

Senate Democrats said the Dulles project can be funded without cutting other projects and accused the McDonnell administration of manufacturing a crisis at VDOT. “In 2004 and 2006, when budget negotiations went on much longer, VDOT did not issue this order,” spokesman Joshua Karp said. “Either Governor McDonnell is not as adept at managing state government as previous governors or he is using VDOT for political purposes. We suspect the latter.”

Colgan did not return phone calls seeking comment. Democrat Sen. L. Louise Lucas (Portsmouth) had considered voting for the budget but said she won’t after realizing the spending plan only includes language, but not money, to ease tolls in Hampton Roads. Transportation Secretary Sean Connaughton said the Commonwealth Transportation Board, not the administration, will allocate the money.

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