Democratic presidential candidate Bernie Sanders has confirmed he did meet the Pope during his trip to the Vatican, saying he was “honoured”.
The brief meeting took place on Saturday morning at Pope Francis’s residence before he left to meet migrants on the Greek island of Lesbos.
Senator Sanders described the Pope as one of the “extraordinary figures… in modern world history”.
An aide said the meeting lasted five minutes and no photographs were taken.
Mr Sanders told Associated Press: “I told him 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.
“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 had been in the Vatican to attend a conference on economy and social justice.
Late on Friday he fulfilled his promise to release his tax return, which showed that he had taxable income of $205,000 (£144,000) in 2014, the majority of it from his Senate salary. He and his wife paid $27,000 tax.
This puts him almost in the top 5% of US earners, Reuters news agency says.
His opponent, Hillary Clinton, and her husband Bill have earned nearly $140m over the past eight years, according to previously released tax returns.
Some political commentators have wondered why he would travel to Rome so close to Tuesday’s crucial New York primary.
“It’s a real misstep,” New York Times columnist Charles Blow said on CNN. “He’s basically going to be saying the same thing there that he’s been saying here.”
Mr Sanders’ campaign manager Jeff Weaver defended the trip at a rally.
“Hillary Clinton has been out of the state on a number of occasions for high-dollar fundraisers,” he said. “We think this is a more important reason to leave the campaign trail for the day.”
Mrs Clinton, who represented the state in the US Senate for two terms, holds a commanding lead in New York, according to recent polls.