Anyone looking to set eyes on Mitt Romney's tax returns any time soon can forget about it -- and will have to take him at his word.

A day after Romney, the presumptive GOP presidential candidate, revealed that he has never paid less than 13 percent of his income in taxes each year for the past decade, President Barack Obama's campaign manager Jim Messina made an offer to Romney to release just five years' worth of his returns in exchange for the president's campaign easing up on the issue.

"If the governor will release five years of returns, I commit in turn that we will not criticize him for not releasing more - neither in ads nor in other public communications or commentary for the rest of the campaign," Messina reportedly wrote to Romney's campaign manager Matt Rhoades.

But Romney's campaign politely declined the offer and "unintentionally" released Messina's email.

Rhoades wrote, "Hey Jim, Thanks for the note. It is clear that President Obama wants nothing more than to talk about Governor Romney's tax returns instead of the issues that matter to voters, like putting Americans back to work, fixing the economy and reining in spending. If Governor Romney's tax returns are the core message of your campaign, there will be ample time for President Obama to discuss them over the next 81 days."

The Democrats have been hammering Romney to make public more than the two years of returns he has provided thus far. However, Romney has remained adamant that the public will see no more than what has already been released.

Romney's refusal to cough up more details of his returns has sparked speculation on what they may contain, including an unsubstantiated accusation that he hasn't paid taxes in years.

Senate Majority Leader Harry Reid has accused Romney of not having paid taxes for 10 years. Reid is yet to fully identify the source of his information even though he has been called on to do so.

Romney has denied Reid's claims and his wife, Ann, has said releasing more information about their family's tax returns would only provide more ammunition for the Democrats.

"Every year, I've paid at least 13 percent," Romney told reporters.

To that Reid's office responded, "We'll believe it when we see it."

"Until Mitt Romney releases his tax returns, Americans will continue to wonder what he's hiding," Reid's spokesman Adam Jentleson told Buzzfeed. "Romney seems to think he plays by a different set of rules than every other presidential candidate for the last thirty years, all of whom lived up to the standard of transparency set by Mitt Romney's father and released their tax returns" for more than two years.