WASHINGTON - Republican presidential candidate Mitt Romney is making campaign promises that could produce an economic miracle - or a more predictable list of broken vows.

Romney said he wants to put the nation on a path to a balanced budget while also cutting an array of taxes, building up the Navy and Air Force, and adding 100,000 active-duty military personnel. He said he would slash domestic spending and reduce tax loopholes but has offered few details.

His comments are raising eyebrows in Congress, long accustomed to easier-said-than-done promises. And even some conservatives have expressed their doubts.

Christopher A. Preble, a vice president for the libertarian Cato Institute, said Romney's promise to push military spending to 4 percent of the national economy would require dramatic increases that would raise, not lower, the federal deficit.

Citing "the absurdity of Romney's plan," Preble wrote recently that the candidate "hasn't said what other spending he will cut, or what taxes he would increase."

"Until he does," Preble wrote, "it is logical to conclude that he plans to pile on more debt."

Romney said he would avoid that problem by making courageous cuts to federal programs if elected.

"I have three major ways that we can get ourselves to a balanced budget," he told voters this month in Warwick, R.I. "Number one is to eliminate some programs. . . .Not just slow down their rate of growth. But look at programs and say, 'Too many, too big, too expensive, too ineffective, get rid of it.' Some programs you're going to like. I'm going to ask for sacrifice. But the sacrifice will not be taking more from your wallet. ... I'm not going to give anybody any free stuff."

Other Romney proposals would make states responsible for programs such as Medicaid, and reduce the federal workforce by 10 percent "through attrition."

It's not uncommon for candidates to promise unspecified spending cuts. Often, however, they find it extremely difficult to fulfill the pledges once elected. That's one reason the nation's debt has soared under Republican and Democratic presidents and Congresses alike.

Romney has shown little willingness to cut popular programs so far. He joined President Obama, and bucked some House Republicans, by backing an extension of low college loan rates for middle-income students, a $6 billion government cost.

Voters may understand that candidates cannot or will not keep all their promises.

"You campaign in fiction, and govern in fact," said Tom Davis, a former congressman who headed the Republicans' House campaign committee from 1998 to 2002.

He noted that Obama quickly backed off his campaign promise to close the Guantanamo Bay prison when he ran into opposition in Congress. Obama also pledged to overhaul immigration laws, which has not happened.

Davis said it's the general thrust of Romney's proposals that matters most, not every specific item.

"What he's trying to do is sketch a different vision," Davis said. Details of how Romney's proposals would pan out, if he's elected, "will be determined by Congress and events," he said.

Rep. Steve LaTourette (R., Ohio) said Romney's proposals "are aspirations" more than firm promises. If elected, Romney may have to revisit his current rejection of tax increases and his vow to leave Social Security and Medicare unchanged for current and soon-to-be recipients, LaTourette said.

Romney and Obama "have to come to the realization that a big deal," which includes tax increases, spending cuts, and changes to Social Security and Medicare, "is the only way" to address the nation's deficit problems, LaTourette said.

Romney has called for a host of tax cuts. Independent analysts say they would worsen the deficit unless offset by deep and politically unpopular spending cuts.

Romney would keep the Bush-era tax cuts and further reduce all marginal income tax rates by 20 percent. He said he would lower the corporate tax rate, eliminate the estate tax, push a balanced-budget amendment to the Constitution, and make $500 billion in unspecified domestic discretionary spending cuts in 2016. He wants wider exploration for energy, including oil drilling in the Arctic National Wildlife Refuge, or ANWR.

Such promises draw loud cheers at GOP rallies. But for decades, Republican-run and Democratic-run Congresses alike have rejected ANWR drilling, a balanced-budget amendment, deep spending cuts, and other mainstays of Romney's campaign.

Whether these campaign ideas are called proposals, aspirations, or promises, they are easier to talk about than to achieve.