Pope Francis has said his brief encounter with US presidential candidate Bernie Sanders was a sign of good manners "nothing more," and hardly evidence of interfering in American politics.
The White House hopeful called it a "real honour" to meet "one of the extraordinary figures" in the world, a kindred spirit on economic inequality, which is a main Sanders campaign theme.
Francis was on his way to Greece to highlight the plight of refugees and Mr Sanders was heading back to New York to resume campaigning when they ran into each other in the lobby of the pope's residence, the Domus Santa Marta hotel in the Vatican gardens.
The Vermont senator was in Rome for a Vatican conference on Friday on economic inequality and climate change.
"This morning when I left, Sen Sanders was there. ... He knew I was leaving at that time and I had the kindness to greet him and his wife and another couple who were with them," the pope told reporters travelling back with him to the Vatican.
"When I came down, I greeted them, shook their hands and nothing more. This is good manners. It's called good manners and not getting mixed up in politics. If anyone thinks that greeting someone means getting involved in politics, they should see a psychiatrist," the pope said.
Earlier, Mr Sanders said that he told the pope that he appreciated the message that Francis was sending the world about the need to inject morality and justice into the world economy. Mr Sanders said that was a message he too has tried to convey.
"We had an opportunity to meet with him this morning," Mr Sanders said. "It was a real honour for me, for my wife and I to spend some time with him. I think he is one of the extraordinary figures not only in the world today but in modern world history."
Mr Sanders said he had the chance to tell the pope that "I was incredibly appreciative of the incredible role that he is playing in this planet in discussing issues about the need for an economy based on morality, not greed".
Mr Sanders and his wife, Jane, stayed overnight at the hotel, on the same floor as the pope. Francis noted to reporters that members of the Vatican conference that Mr Sanders had attended also were staying at the hotel.