Obama meets Pope Francis in Vatican City

President Barack Obama held nearly an hour of private talks about the global situation with Pope Francis on Thursday and invited the pontiff to visit the White House.

Obama appeared at ease and joked with the pope during the parts of their first meeting that were open to reporters, at one saying he did not know how his wife and children "put up with me".

The president and his delegation, including Secretary of State John Kerry, walked past the frescoed halls of the Vatican's Apostolic Palace to the entrance of the Francis' private library.

There were no immediate details of what they discussed, but in the run up to the meeting, Obama had given an interview to an Italian newspaper praising the pope's commitment to addressing growing gaps between rich and poor.

"It is a great honor. I'm a great admirer," the president said as the pope greeted him and they sat at the pontiff's desk. "Thank you so much for receiving me."

Obama invited the pope to visit the White House as he was giving Francis a symbolic gift of seeds of fruit and vegetables from the garden of the presidential residence.

The White House said other seeds would be donated in the United States that will yield several tons of produce to a charity of Pope Francis' choosing.