U.S Republican presidential hopeful Mitt Romney said Sunday that he will release his 2010 tax returns and 2011 estimates on Tuesday, acknowledging it was a mistake for his campaign not to have done so earlier.

Stung by a loss to Newt Gingrich in Saturday's South Carolina primary on Saturday, the former Massachusetts governor and venture capitalist said it was "not a good week for me" and he cited all the time he had spent talking about his tax returns as his rivals pressed him to make them public.Ad

After months of resistance, Romney had said last week that he would release tax information for 2011, but not until April, close to the tax filing deadline. That also was seen as a time, before the South Carolina race rattled his front-runner status, when the GOP nomination might have been decided.

"I think we just made a mistake in holding off as long as we did," Romney told Fox News.

Romney disclosed last week that, despite his wealth of hundreds of millions of dollars, he has been paying in the neighborhood of 15 percent, far below the top maximum income tax rate in the United States of 35 percent.

Releasing the returns " will provide, I think, plenty of information for people to understand that the sources of my income are exactly as described in the financial disclosure statements we put out a couple of months ago," Romney said.

During 2010 and the first nine months of 2011, the Romney family had at least $9.6 million US in income, according to a financial disclosure form submitted in August.

Further focusing attention on his wealth was Romney's offhand remark to reporters that his income from paid speeches amounted to "not very much" money.

In the August disclosure statement, he reported being paid over $373,000 for such appearances for the 12 months ending last February. That sum alone would him in the top one per cent of U.S. taxpayers.

In addition, Romney owns investments worth between $7 million and $32 million in offshore-based holdings, which are often used legitimately by private equity firms to attract foreign investors.

Such offshore accounts also can enable wealthy U.S. investors to defer paying taxes on some assets, according to tax experts.