WASHINGTON (AFP) - United States (US) President Barack Obama expressed strong admiration of Pope Francis for promoting "a true sense of brotherhood and sisterhood and regard for those who are less fortunate", in an interview aired on Friday.

"I have been really impressed so far with the way he's communicated what I think is the essence of the Christian faith," Mr Obama told CNN of the pontiff who has refashioned the image of the Roman Catholic Church since his installation last year.

The US president, who will visit the Vatican in March, said he didn't believe Pope Francis was acting out of a desire to gain widespread approval.

Rather, "I think he is very much reflecting on his faith and what he needs to do to make sure that folks - not just of the Catholic faith but people all around the world - are living out a message that he thinks is consistent with the lessons of Jesus Christ," Mr Obama said.

"That's a meeting I'm looking forward to," he added of the planned Mar 27 sit-down.

Mr Obama has made rising inequality and the struggles of America's middle classes the signature domestic issue of his second term.

In a speech in December, Mr Obama praised an argument advanced by Pope Francis, the first non-European pontiff in nearly 1,300 years, on rising inequality in societies split between the very poor and the super rich.

"How could it be, he wrote, that it's not a news item when an elderly homeless person dies of exposure, but it is news when the stock market loses two points?" Pope Francis argued in the exhortation, that such conflicted values marked a "case of exclusion" in an unequal society.

And in October, the president told CNBC that he was "hugely impressed" with the pope's humility and empathy to the poor.

Mr Obama was last in Vatican City in 2009, when he met Pope Benedict.