A senior adviser for Mitt Romney’s campaign is defending the GOP nominee against criticisms that his tax-cutting plan lacks specifics about which deductions and loopholes he would close.

Romney has vowed to cut income tax rates across-the-board by 20 percent but has not provided details about which specific deductions and other tax code provisions he’d seek to scuttle to pay for the plan.

“To start negotiating in a campaign environment, you are going to lock in Republicans, you are going to lock in Democrats,” Romney adviser Ed Gillespie said on Fox News Sunday.

He said Romney, if elected president, would instead work with Democrats to flesh out specifics. “Gov. Romney has a proven record of being able to work across the aisle,” Gillespie said.

Both campaigns have traded charges of dishonesty over Romney’s tax reform proposals, with Democrats pushing the GOP candidate to release more specifics. 

President Obama in the first debate with Romney charged that his tax plan called for a $5 trillion cut and would force the middle class to shoulder a greater burden while worsening the deficit.

Romney’s campaign, though, disputes the $5 trillion figure and says the plan would bring more revenues to help ease the deficit. Romney has rebuffed calls to share more details until he can sit with lawmakers to discuss his proposal.