(Read more: Pope urges Davos elite to serve humanity with wealth)
"In the United States over the last few decades, we've seen a growing gap between the income of those at the very top and the income of the typical family," he said.
"But this isn't just a problem for the United States, it's a problem for countries around the world. And it isn't just an economic issue, it's a moral issue."
As he arrived at the Vatican, Obama and his delegation were led past the ceremonial Swiss Guard through a richly frescoed hall before being escorted into a room where he and the pope shook hands warmly.
Since his election a year ago, Pope Francis has several times criticized unbridled capitalism, the excesses laid bare by the global financial crisis, and the growing gap between the rich and poor, even in developed countries.
(Read more: Not Just Talk: Pope Francis Cleans Up Finances in First Year)
Obama has repeatedly praised the pope for his compassion and emphasis on helping the poor, and the meeting could help to give impetus to some of his initiatives back home, such as boosting the middle class and helping low-income Americans succeed.
In the interview, Obama said globalization and greater trade and commerce had lifted hundreds of millions of people out of poverty in recent decades. "But the pope is correct when he says that not enough people are sharing in that progress, and too many people are being left behind."
The center of Rome was blocked off for Obama's visit, which was to include a meeting with Italian President Giorgio Napolitano and Prime Minister Matteo Renzi later in the day.
When Obama met Francis's predecessor, Pope Benedict, in 2009, Benedict raised the matter of abortion, a sensitive issue for many U.S. Catholics as the Church considers abortion a grievous sin. Obama promised to do everything he could to reduce the number of abortions.
Francis, while giving no hint of changes to church doctrine, has used softer language than his predecessor on the rights of women and gays, a stance that has also resonated with Obama, who counted on both groups to help propel him to the presidency in 2008 and 2012.
(Read more: Pope as a pin-up? Francis gets his own fan magazine)
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