Mitt Romney today outlined a plan that he said would restore "freedom" to the American economy, dramatically cutting taxes and spending to "deliver more jobs, less debt, and smaller government."

"I am running for President because I have the experience and the vision to get us out of this mess," he said in a speech at the University of Chicago. "I am offering a real choice and a very different beginning."

But President Obama's re-election campaign says Romney's plan and vision are sorely lacking in fine print.

"Gov. Romney repeated today that he intended for his tax plan to be revenue-neutral. But independent parties put the cost of his tax plan at $5 trillion over 10 years," said Obama for America policy director James Kvaal on a conference call with reporters. "So if the governor has plans to eliminate tax deductions and tax exemptions to pay for that cost, he should put those proposals on the table."

Romney has said he would lower tax rates across the board, including cutting the top marginal rate from 35 to 28 percent, middle rates from 25 to 20 percent, and the lowest bracket from 10 to 8 percent.

But he has not clearly articulated how the lost revenue would be fully offset so as not to blow a hole in the federal budget.

There are "lots of unanswered questions," said Obama campaign spokesman Ben LaBolt.  "His tax proposal can't be scored. He hasn't outlined how he's going to pay for it, he says he has to work it out with Congress. So is he going to increase the deficit by $5 trillion or is he hiding how he's going to raise taxes?"

To keep his tax cuts revenue-neutral, Romney has proposed broadening the tax base by eliminating some loopholes and deductions, but hasn't said which ones.  He would also sharply curtail federal subsidies for some programs - including Amtrak, public broadcasting and family planning grants to Planned Parenthood - but hasn't offered a comprehensive list.

The non-partisan Tax Policy Center has estimated, based on publicly available details, that Romney's tax plan would add $900 billion to the federal deficit in 2015.

The Romney campaign disputes the estimates, however, insisting that robust economic growth spurred by the tax cuts would in turn yield higher tax revenues overall, thereby offsetting the cost of the initial cuts.