Bernie Sanders said he would always regret it if he missed a chance to meet the Pope, as he plans to leave New York just days before a key primary in order to speak at a Vatican conference.

Sanders is giving a 15 minute speech in Rome and there is no guarantee that he will meet the Pontiff.

"I would be kicking myself forever if I did not seize the opportunity," he said about having an audience with the Pope in an interview with the Washington Post.

"It's something I would be very proud to see happen," he added.

"I believe that the Pope has been an inspirational figure in raising public consciousness about the kind of income and wealth inequality we are seeing all over the world."

The trip carries a political risk, as Sanders is leaving the campaign trail just days before a crucial primary in New York.

"It's absolutely worth the trip to participate in a conference under a Pope who has led the world in raising consciousness on the most important issues of social, economic and enviromental justice," he said.

Theologian and US politics specialist Chad Pecknold suggested that the trip might actually give weight to Sanders on the international stage.

"Let's say that he is realistic and that his path to the nomination is extremely slim," the professor at The Catholic University of America told The Washington Post.

"Then he must say, 'Well, what is my role after this campaign?' It seems clear that he is in a position now to highlight his new profile."

Sanders' chief strategist, Tad Devine, denied there are political implications for his speech, however.

"It's not going to be a political speech or event. We're not viewing this through a political lense," he said.

Sanders is not the only American politician travelling to the Vatican in upcoming weeks. Joe Biden, America's first Catholic vice president, is visiting the country on April 29.

Biden will address a major conference on the progress of regenerative medicine in Vatican City, speaking on his campaign to cure cancer.

The gathering, championed by Pope Francis, will be part of Biden's three day trip to Rome and the Vatican. A meeting with the Pope has yet to be determined, according to his office.