Bernie Sanders will take a break from the campaign trail to speak at the Vatican on social, economic and environmental issues.

The democratic senator, who has likened his views to the Pope's, will go to Rome to speak at a conference hosted by the Pontifical Academy of Social Sciences, after a debate with Hillary Clinton on April 14.

Sanders, who often quotes Pope Francis, is thought to be the only American public official speaking at the conference.

"I think the Vatican has been aware of the fact that, in many respects, the Pope's views and my views are very much related," said Sanders.

"He has talked in an almost unprecedented way about the need to address income and wealth inequality, poverty and to combat the greed that we're seeing all over this world, which is doing so much harm to so many people. ... For me, it is an extraordinary honour to receive this invitation."

Sanders said he will be speaking on "an issue that is very dear to my heart, which is how we create a moral economy that works for all of the people rather than just the top one per cent.

"I will also in my remarks be addressing the planetary crisis of climate change and the moral imperative to make sure we leave this planet in a way that is healthy and habitable for future generations," he added.

Sanders' trip comes four days before the New York primary on April 19, a state that both Sanders and his rival Hillary Clinton see as home turf and are keen to win.