Fairfax County's top administrator is warning residents that impending budget shortfalls will inevitably force cutbacks and changes in the services and programs to which they've grown accustomed.

Speaking to residents in an online question-and-answer session Thursday, County Executive Ed Long said a lagging economy and across-the-board reductions in the federal budget could endanger "the quality of life that we have come to expect here."

To combat what some officials said could be a $100 million-a-year shortfall in county budgets over the next three years, Fairfax may be forced to raise taxes or even eliminate county programs and positions, he said.

Among those county services immediately at risk are late-night library hours and portable bathrooms at athletic facilities, county officials say. But a list of specific cuts won't be ready until January, when deep federal spending cuts are set to take effect if Congress fails to strike a new deficit deal.

The Office of Management and Budget said the $1.2 trillion in automatic cuts to federal spending would be "deeply destructive." And with an economy heavily dependent on federal spending, Fairfax could be facing massive cuts in social services should the cuts kick in.

To cope with the possible loss of revenue, Long has asked county agencies to plan for budget cuts up to 10 percent over the next two years. County Supervisor Pat Herrity, R-Springfield, said, however, that it is time for Fairfax to make real cuts instead of "nibbling around the edges."

The county needs to re-evaluate some of its agencies and some of the jobs it now fills to determine whether they're necessary, Herrity said, adding that across-the-board cuts "make no sense."

"We need to cut our nice-to-haves and not our need-to-haves," Herrity said. "We have a real spending problem."

County Board of Supervisors Chairwoman Sharon Bulova wouldn't rule out a review of all county agencies and departments, but said she was still considering the board's options. Until hearing Long's proposed budget, Bulova said the board would continue to make careful decisions and look for ways to work more efficiently.