But Frank argued that this would unfairly target Medicare and Social Security.

"I urge you to make clear that Defense Secretary Leon Panetta did not speak for the Administration when he stated yesterday that additional spending cuts, beyond those in the recent debt-ceiling agreement, should come from non-discretionary spending such as Social Security and Medicare while the military budget is spared," Frank wrote.

He said Panetta's comments seem to reveal a Pentagon strategy to keep U.S. troops in Iraq past 2011 and "resist an orderly withdrawal from Afghanistan."

"Secretary Panetta's recommendations would require reducing Social Security benefits and medical care for older Americans," Frank wrote. "A sensible approach to military spending would allow America to remain the strongest nation in the world without requiring us to put additional burdens on older citizens of our own country."