Washington - In the wake of President Barack Obama's appeal to Congress to stave off across-the-board military and domestic spending cuts, Defense Secretary Leon E. Panetta warned Wednesday that reductions from the automatic cuts would curtail U.S. naval operations in the western Pacific by as much as a third and force one-month furloughs for as many as 800,000 Defense Department civilian employees starting this spring.

"This is not a game, this is reality," Panetta said emphatically in a speech at Georgetown University, one of his last as defense secretary, in which he blasted Congress for what he said was its failure to live up to its responsibilities. "These steps would seriously damage the fragile American economy, and they would degrade our ability to respond to crisis precisely at a time of rising instability across the globe."

He added, "This is no way to govern the United States of America."

Panetta has been warning in dire terms for months about the effects of the across-the-board cuts, but defense budget analysts have viewed a number of his admonitions as hyperbole meant to prod Congress into making a budget deal. On Wednesday, analysts said Panetta meant it this time.

"These are real, legitimate impacts," said Todd Harrison, an analyst at the Center for Strategic and Budgetary Assessments, a research group in Washington. Under sequestration, the Pentagon would have to cut nearly $50 billion, or about 9 percent, of current military spending by Oct. 1.

The potential cutbacks in naval operations in the western Pacific are particularly striking since they would undermine what the Obama administration has promoted as a critical part of its defense strategy - a "pivot," or rebalancing, of forces to the Asia-Pacific region to counter the increasing assertiveness of China's military.

Navy officials said Wednesday that they were considering cutbacks throughout the 7th Fleet area of operations, which encompasses more than 48 million square miles and ranges from the Korean Peninsula to Guam to Australia and beyond. The officials said that the cuts would potentially reduce the number of ships, aircraft, joint military exercises and personnel in the region.

The furloughs would potentially begin as early as April and would cut one work day a week from the Pentagon's vast civilian work force for the next six months. The employees would face a corresponding 20 percent cut in pay, which Panetta said would have a substantial negative effect on the economy.

Panetta said the across-the-board cuts would also force the Pentagon to reduce training and maintenance for the Army, including putting two-thirds of active-duty brigade combat teams outside Afghanistan at "reduced readiness levels." Army officials said Wednesday that this would mean less training at Army bases like Fort Irwin, Calif., and Fort Polk, La., for troops prepared to respond to crises around the world.

The Pentagon's current annual operating budget for the fiscal year that ends Sept. 30 is $534 billion, with an additional $88 billion largely for the cost of the war in Afghanistan. The across-the-board cuts would apply to the total of $622 billion, along with some additional funds that have not been spent in previous years.

Panetta, a former chairman of the House Budget Committee and a former White House budget director under President Bill Clinton, has frequently expressed exasperation about the current climate on Capitol Hill.

"My fear is that there is a dangerous and callous attitude that is developing among some Republicans and some Democrats that these dangerous cuts can be allowed to take place in order to blame the other party for the consequences," he said.