Sen. John McCain, R-Ariz., said the Army was being unfairly targeted for cuts.
"As a Navy man, I do," he said to reporters, joking that it was a "rare thing" for a former member of the Navy to say.
The Army is facing proposed cuts that would reduce its force to the smallest size since before World War II.
Cutting the numbers of Army personnel, McCain warned, would severely damage the country's military readiness.
Sen. Roy Blunt, R-Mo., added that he had "real concerns" about the proposal, pointing out that it had more to do with Obama's budgetary priorities than any real concern about defense.
"I don't think there's been any analysis as to what we actually need as opposed to just the military be given a line item saying you know, 'make it work,'" he said.
Sen. Lindsey Graham, R-S.C., said that he was "shocked" by the Pentagon's announcement.
"This is really quite frankly a dumb idea," he said, suggesting that the move would hurt the country's ability to respond to a threat.
"Having an army that small just doesn't meet our defense needs, and you can't pick what wars you're going to fight. You have to be ready to deter war," he said.
Even Sen. Tom Coburn, R-Okla., a supporter of military spending cuts, pointed out that these cuts were hurting the troops, not cutting bureaucratic waste in the Defense Department.
"What they're doing is cutting troops, the people that defend us, and cutting real expenditures on real material and training and leaving in place the inefficiencies and the incompetence," he said.