The Obama campaign is calling on Mitt Romney to release five years of his tax returns, and promises it will end its criticism on the issue if Romney does so.

The latest chapter in the tax battle came in a letter from Obama campaign manager Jim Messina, who made the offer. 

"Gov. Romney apparently fears that the more he offers, the more our campaign will demand that he provide," Messina wrote to Romney campaign manager Matt Rhoades. "So I am prepared to provide assurances on just that point: 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."

Rhoades responded by suggesting Obama's campaign shouldn't be so preoccupied with Romney's tax returns in the face of the country's other pressing issues.

"It is clear that President Obama wants nothing more than to talk about Gov. 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," Rhoades wrote back to Messina on Friday. "If Gov. 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 Obama campaign has made repeated calls for Romney to release more years of his personal tax returns, but Romney has maintained that he has met required transparency standards and that releasing more would only lead to additional attacks. 

Senate Majority Leader Harry ReidHarry Mason ReidSenate GOP breaks record on confirming Trump picks for key court Don’t worry (too much) about Kavanaugh changing the Supreme Court Dem infighting erupts over Supreme Court pick MORE (D-Nev.) has also charged Romney with not paying taxes for 10 years, on the basis of what he called a credible but anonymous source. Republicans have offered heavy criticism of Reid, who has provided no evidence to back up his claims. 

Democrats see the issue as benefiting President Obama. They have worked hard to portray Romney as out of touch with the middle class, and they believe his wealth, magnified by his personal tax records, will underline their argument. 

Because most of Romney's income is derived from capital gains, which are taxed at a lower rate than income, he pays a lower tax rate than many middle-class workers.

Romney on Thursday waded into the tax debate again.

“I did go back and look at my taxes and over the past 10 years I never paid less than 13 percent,” Romney told reporters in South Carolina on Thursday. “I think the most recent year is 13.6 or something like that, so I paid taxes every single year.”

Romney is not required to release his personal tax returns, but it has become tradition for presidential candidates to do so. Obama's campaign has repeatedly invoked Romney's father, George Romney, who released 12 returns, as an example. 

"In the governor's case, a five-year release would appropriately span all the years that he has been a candidate for president," Messina wrote. "It would also help answer outstanding questions raised by the one return he has released to date, such as the range in the effective rates paid, the foreign accounts maintained, the foreign investments made and the types of tax shelters used." 

Romney voluntarily released tax returns from 2010 as well as an estimated return for 2011 earlier this year, which showed he paid just under a 14 percent tax rate.

This story was posted at 7:21 a.m. and updated at 9:24 a.m.