WASHINGTON — Republicans now controlling the House promised Thursday to slash domestic agencies' budgets by almost 20 percent for the coming year, the first salvo in what's sure to be a bruising battle over their drive to cut federal spending to where it was before President Barack Obama took office.

"Washington's spending spree is over," declared Paul Ryan, the Budget Committee chairman who announced the plan. "The spending limits will restore sanity to a broken budget process," he said, returning "to pre-stimulus, pre-bailout levels."

But Republicans won't get everything they want. Democrats control the White House and the Senate, and even Republicans in the stoutly conservative House may have second thoughts when the magnitude of the cuts sinks in.

The White House says the cuts could lead to widespread furloughs of federal employees and force vulnerable people off subsidized housing, reduce services in national parks and slash aid to schools and local police and fire departments.

The House Republicans are seeking to keep their campaign promise to cut $100 billion from domestic programs. The initial cuts would be approved over coming weeks as Congress wraps up the long-overdue 2011 budget; the second stage would come as the House GOP advances a fresh round of spending bills for fiscal 2012, which begins Oct. 1.

The hardest hit agencies would include the Food and Drug Administration, the IRS and the departments of Commerce, Housing and Urban Development and Agriculture, according to partial details released by the House Appropriations Committee. Foreign aid on an annualized basis would bear a relatively modest 6 percent cut. Congress' own budget would be barely touched.

Conservative Republicans want even greater cuts, and they'll be given the chance to impose them in a freewheeling floor debate scheduled for the week of Feb. 14.

In Thursday's plan:

— The Department of Homeland Security would face a budget freeze instead of the modest 3 percent hike proposed by Obama.

— Rapidly growing spending on veterans' health care appears likely to be largely untouched.

— Republicans would scale back Obama's proposed 4 percent, $23 billion increase for the Pentagon. Instead, the military budget would grow by just $10 billion, a 2 percent increase.

— Health research and federal aid to local school districts appear likely to bear a relatively small share of the pain when lawmakers draw up a massive spending bill for the departments of Education, Labor and Health and Human Services.

Republicans made a campaign promise to cut $100 billion from Obama's request for domestic agencies such as the Department of Education, for the budget year that began last October. But since the year is well under way, they're so far falling short, just $58 billion under the plan released Thursday. They promise to try to fully impose the dramatic cuts during what is sure to be a contentious debate.

The $100 billion in reductions was an inflated promise since it was measured against Obama's budget request for this year. The actual savings would be less since Obama's budget boosts were never approved, and the government is operating at 2010 levels. Instead, the savings from domestic programs in making the switch from 2010 to 2008 — if carried out over a full year — would be about $86 billion, imposing cuts on domestic agencies of 19 percent on average.

Republicans acknowledge they can achieve, at best, $35 billion in overall savings by the Sept. 30 end of the year after the Pentagon receives its small budget boost.

A stopgap spending bill passed in December expires March 4. Enacting a full-year funding bill promises to be a difficult test of the new balance of power in Washington. Republicans control only the House, but Democrats acknowledge that — with the deficit on pace to hit $1.5 trillion this year — some spending cuts will have to be made.

"We're not burying our heads on the sand. We recognize that we have to do something," said Senate Majority Leader Harry Reid, D-Nev., Obama's most powerful ally on Capitol Hill.

Republicans say some agencies like the FBI, the Indian Health Service and NASA are unlikely to be cut all the way back to pre-Obama levels. But that means other agencies, like the Environmental Protection Agency, would have to bear even bigger cuts.

Returning to 2008 levels would produce dramatic reductions for many agencies: a 41 percent cut for EPA clean water grants; an 8 percent cut to NASA, a 16 percent cut for the FBI and a 13 percent cut in the operating budget of the national parks.

The hard-charging GOP freshman class — especially newcomers from Minnesota, Wisconsin, New York and New Hampshire — may have some second thoughts when confronted with big cuts to the Low-Income Home Energy Assistance Program, known as LIHEAP, which provides home heating subsidies to the poor.

Republicans in Texas, Florida and Alabama — where NASA facilities mean thousands of jobs — are sure to fight against cuts to the space agency. NASA could have to abandon the International Space Station, the White House warns.

Lawmakers in both parties from rural districts are likely to resist cuts to a program that subsidizes service by smaller airlines to isolated cities and towns like Scottsbluff, Neb., and Burlington, Iowa. Smaller subsidies or tighter rules would probably mean some communities would lose service.

It's unclear so far how Republicans will treat particularly sensitive programs, including Pell Grants for low-income college students and the Women, Infants and Children program, which provides food for low-income pregnant women, mothers and young children.