Pope Francis has begun his tour of the U.S., where he is expected to greet millions of American Catholics and address thorny issues like climate change and income inequality, BBC News reports.

U.S. President Barack Obama welcomed the pope as he landed on Tuesday, September 22 - a rare honor for a foreign dignitary.

The pontiff will visit Washington DC, New York and Philadelphia.

On the trip from Cuba to the US, the Pope held a news conference and answered those who said his criticisms of capitalism went too far.

"I've never said anything that is not in the social doctrine of the church," the Pope told reporters. "Maybe I have given the impression of (being) a bit lefty, but that would be a mistaken interpretation."

When he landed at Andrews Air Force Base, the Pope was greeted by Obama and his family along with Vice-President Joe Biden and his wife.

Taking questions from journalists, the Pope answered in Spanish and Italian for almost half an hour, apologizing that English was not his forte.

Asked why he hadn't met dissidents in Cuba, he said he had had no private audiences with anyone. However, he had greeted all those invited to meet him on the steps of Havana Cathedral - who may have included dissidents. Now, Pope Francis is starting to focus on the US leg of his visit - which could be just as tricky a diplomatic balancing act.