UPDATE 3-Romney paid at least 13 pct tax rate over 20 years -letter

* Romney paid 14.1 percent tax rate in 2011

* Stands firm in refusing to release earlier returns

* Says he paid taxes annually over 20 years

By John Whitesides

WASHINGTON, Sept 21 (Reuters) - Republican presidential candidate Mitt Romney fought back on Friday against Democratic charges he paid no taxes in some years, releasing a letter from his accountants saying he paid an effective federal tax rate of at least 13.6 percent annually over 20 years.

Despite heavy political pressure, Romney stood firm in refusing to make those returns public, but followed through on an earlier promise to release his 2011 return. It showed he paid $1.9 million in taxes on more than $13 million in income - an effective tax rate of 14.1 percent.

Senate Democratic leader Harry Reid and others have questioned whether Romney paid taxes in at least some of those earlier years. President Barack Obama has used Romney's refusal to release more returns as support for his argument that his challenger is out of touch with the lives of everyday Americans.

Romney, who faces Obama in the Nov. 6 election, earns the majority of his income from investment profits, dividends and interest that is taxed at a lower rate than wage income, which is taxed at a top rate of 35 percent.

The tax release on Friday afternoon, traditionally a time when politicians make public information they hope will not attract heavy news coverage, came after a brutal week for Romney's presidential campaign.

A secretly recorded video was released earlier in the week showing Romney denigrating the 47 percent of Americans who would back Obama "no matter what" as government-dependent victims who pay no taxes. That followed last week's fumbled response to attacks on U.S. compounds in Libya and Egypt.

Romney, a former governor of Massachusetts, has fallen slightly behind Obama in polls in the White House race, with a series of three high-stakes debates between the two scheduled in October.

Even many of Romney's Republican allies have suggested he release his earlier returns to end the controversy. Romney released his 2010 return in January, which showed he paid an effective tax rate of 13.9 percent, and had promised to release his 2011 return before the election.

The 2011 return made public on Friday showed Romney donated about $4 million to charity in 2011, amounting to nearly 30 percent of his income.

Romney has refused to release returns from his years as head of Bain Capital, a private equity fund that Democratic critics have charged plundered companies and cut jobs in a quest for profits. Romney has an estimated net worth between $190 million and $250 million.

MORE TO 'DISTORT AND LIE ABOUT'

He has said that issuing full returns from earlier years would just give Democrats "hundreds or thousands of more pages to pick through, distort and lie about."

The Obama campaign has repeatedly criticized Romney for his refusal, and released an ad earlier in the year questioning the decision and noting Romney's accounting techniques and tax havens to minimize his tax burden.

The Romney campaign published a statement on Friday from former Internal Revenue Service Commissioner Fred Goldberg, who declared the returns "reflect the complexity of our laws and the types of investment activity that I would anticipate for persons in their circumstances."

Goldberg said, "In my judgment, they have fully satisfied their responsibilities as taxpayers."

The letter from accountants PricewaterhouseCoopers said the average of Romney's annual effective federal personal income tax rate during the 20-year period up to 2009 was 20.2 percent, and he and his wife, Ann, had a charitable deduction rate of 13.45 percent.

The campaign also released a letter from Romney's doctor noting he was in excellent health, but occasionally needed to use an inhaler to ease an obstruction in his airways.