Under renewed pressure from the Obama campaign to release additional tax information, Mitt Romney's campaign showed no signs of buckling Friday morning.

The former Massachusetts governor's top spokesman, Eric Fehrnstrom, told MSNBC that the campaign considered the material put out so far to be "sufficient." Romney had, he noted, complied with "all of the disclosure that is required by law." In addition, he had "voluntarily put forward hundreds of pages in tax returns."

While hundreds of pages of returns sounds like a lot, it constitutes just one year of tax filings: the 2010 forms that Romney produced in late January. Romney also released an estimate for 2011, which the campaign (as Fehrnstrom confirmed) would supplement with a full report when it was ready. Beyond that, however, there would be nothing further.

"We have already put out hundreds of pages of tax return information," Fehrnstrom repeated during his interview.

This, of course, won't put the issue to bed. A front-page Washington Post story on Romney's secretive personal financial disclosure filings has put new attention on his earnings. And on Thursday evening, the Obama campaign began what appears to be a sustained effort to ramp up the pressure for more disclosure.

"Governor Romney provided 23 years worth of tax returns to the McCain campaign so they could determine if he would make a suitable Vice President," Obama campaign manager Jim Messina said in a statement. "He must meet that same standard now so that the American people may judge whether he would be a suitable President, and whether there are any conflicts of interest that could cloud his judgment."

Earlier on HuffPost: