The Virginia General Assembly will adjourn its 60-day session Saturday without passing a state budget because of partisan disputes over spending and power.

Legislative leaders acknowledged Friday that members will need to return to Richmond for a special session to adopt a budget by July 1, the start of the fiscal year. Failure to adopt a budget by then could result in a partial government shutdown.

A dozen negotiators from the House of Delegates and the Senate will attempt to hash out a compromise on the two-year, $85 billion budget before all 140 lawmakers return for a vote, likely on March 21.

“We have tried about every other option,” said House Majority Leader M. Kirkland Cox (R-Colonial Heights). “We’re at the point now where we’re out of time.”

In recent days, a slew of groups, from sheriffs to businesses to local governments, have urged lawmakers to reach a deal— any deal — on the budget to avoid potential layoffs, a halt in government services and damage to the state’s vaunted AAA bond rating.

“Without a budget, Virginia’s reputation as a stable, reliable partner for business could be damaged,” said Barry DuVal, president of the Virginia Chamber of Commerce.

Democrats in the Senate have voted down two budgets and threatened to scuttle a third after Republicans failed to give them more power in the equally divided chamber.

November’s elections left the Senate with 20 Republicans and 20 Democrats, but the GOP was able to take control, stacking crucial committees in its favor, because Lt. Gov. Bill Bolling (R) has the power to break some tie votes. He cannot, however, vote on the budget. Democrats have tried to use the budget stalemate to press for more committee seats, but so far, Republicans have refused.

Along with more committee power, Democrats are seeking additional spending outlined in a list this week. It includes $300 million for the second phase of Metrorail’s new Silver Line to Dulles Airport; $65 million for Northern Virginia schools to attract non-teaching staff in that high-dollar job market; and an increase in the gas tax at the rate of inflation.

A relatively small but politically charged item on the wish list is nearly $600,000 to reimburse the University of Virginia the cost of legal fees for successfully fighting off Attorney General Ken Cuccinelli II’s demand for global-warming documents.

“I refused to be bullied or intimidated into voting for a budget that was not in the best interests of the people I represent,” said Sen. Mark R. Herring (D-Loudoun).

Gov. Robert F. McDonnell (R) and legislative leaders say the Democrats’ last-minute demands are unhelpful and unrealistic because they call for additional spending of more than $600 million over the next two years.

“This is the way of delay seen in Washington, D.C., not Richmond,” McDonnell wrote in a letter to Democrats on Friday. “You and I know that all of these differences could have been handled within the confines of the General Assembly if that is what you really desired.”

The House and Senate voted unanimously Friday to carry over the budget bills into a special session. They will officially call the special session on Saturday.

“If everybody goes home for a few days, I think the emotions will ebb a little bit,” said Senate Majority Leader Thomas K. Norment (R-James City). “More importantly, I think all 40 of us will have a chance to hear from our neighbors and citizens.”

Senate Minority Leader Richard L. Saslaw (D-Fairfax) said having budget negotiations extend beyond the regular session is not new. “We’ve had special sessions for — 2001, 2004, 2006 — three of the last 10 years,” he said. “It’s no big deal.”

Negotiators from the House and Senate began meeting Tuesday in small groups on the key issues, including education and health care. But the two Democrats who are part of the Senate negotiating team said their caucus still opposes the budget, which has been approved only by the Republican-controlled House.