U.S. President Barack Obama and his wife, Michelle, paid more than $162,000 in taxes last year, a federal tax rate of 20.5 percent on their income of nearly $790,000.

The White House released the president's tax returns Friday, amid a debate over tax rates that has become a key issue in this year's U.S. presidential race.

President Obama and Vice President Joe Biden have been calling this week for a minimum 30 percent tax rate for millionaires, known as the “Buffet Rule.” The plan would raise income taxes on people earning at least $1 million. It is named for billionaire investor Warren Buffet, who has said it is not fair he pays a lower tax rate than his secretary.

President Obama's likely Republican rival in November's presidential election, multi-millionaire Mitt Romney, paid an effective tax rate of 13.9 percent in 2010.

The White House says the Obamas earned about half their income from Mr. Obama's $400,000 presidential salary, while the other half came from sales of his books.

The Obamas also reported donating more than $172,000 last year to 39 different charities.