In an appearance on CBS' "Late Show with David Letterman," the president suggested Romney was "writing off a big chunk of the country" with comments that 47 percent of Americans "believe that they are victims, who believe the government has a responsibility to care for them."
Romney's comments emerged Monday with the release of a video of his address to campaign donors in Florida in May.
"When I won in 2008, 47 percent of the American people voted for John McCain," Obama said Tuesday in an interview with Letterman to be televised Tuesday night. "They didn't vote for me and what I said on election night was: 'Even though you didn't vote for me, I hear your voices, and I'm going to work as hard as I can to be your president.'"
Obama said people he meets as he travels the country believe in "the American dream."
"There are not a lot of people out there who think they're victims," he said. "There are not a lot of people who think they're entitled to something."
Romney has defended his remarks as "not elegantly stated."
In an interview Tuesday with Fox News Channel, he largely reiterated comments he made at a hastily called Monday night news conference in Costa Mesa, Calif., that his comments addressed "a question about direction for the country."
The question is, "Do you believe in a government-centered society that provides more and more benefits? Or do you believe instead in a free-enterprise society where people are able to pursue their dreams?" he told reporters.
"We have a very different approach, the president and I, between a government-dominated society and a society driven by free people pursuing their dreams," Romney said.