Obama, traveling with Secretary of State John Kerry, arrived at the Vatican on Thursday. He was led through the Apostolic Palace to the pope's study by the Swiss Guards and ceremonial attendants known as Papal Gentlemen.

"It is a great honor. I'm a great admirer," Obama said. "Thank you so much for receiving me."

The US president also expressed his admiration in an interview with the Corriere della Sera newspaper published on Thursday.

"The Holy Father has been an inspiration to people around the world, including me," Obama told the paper, before cautioning that this "doesn't mean we agree on every issue." The president focused in the interview on Francis' repeated calls to combat poverty around the world, an area where they are liable to find consensus.

After their meeting, Obama invited Francis to visit the the White House.

Shared focus on poverty

"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," Obama 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."

Francis addressed the issue of poverty shortly before Obama's arrival as well, warning 500 Italian politicians against becoming "hard-hearted" or "corrupt" during a special Mass on Thursday.

Obama visited Francis' predecessor, German-born Pope Benedict XVI in 2009. Although cordial, that encounter highlighted the gulf between the White House and the Vatican on issues like contraception and abortion. Obama's signature Affordable Care Act, more commonly called "Obamacare," has since courted Catholic criticism for a provision requiring that large companies include contraception in their employees' health insurance.

Some foreign policy frictions might also endure; Pope Francis, born Jorge Mario Bergoglio, had spoken out against a proposed US military intervention in Syria last year.

First the pope, then the prime minister

A survey published last month by CBS News and the New York Times put Obama's approval rating at just 41 percent. Meanwhile, the first Latin American pope is enjoying broad global popularity comparable to that enjoyed by Obama in his first months in office. Among other international accolades, Francis was named Time Magazine's "Person of the Year" for 2013. He recently marked one year in the post.

The Vatican visit follows three days of tricky diplomacy for Obama, meeting European leaders and seeking a common path to deal with the situation in Crimea.

The US president also met with Italian Prime Minister Matteo Renzi, who took up the post last month. Obama in his interview praised Renzi for choosing Tunisia as the destination for his first foreign trip as premier, highlighting Italy's "critical role" in the Mediterranean region.

msh/kms (AFP, AP, Reuters)