
Marcelo Sanchez Sorondo's personal invitation to Sanders was reported by Corriere della Sera newspaper and Radio Vatican.
Sanders will take part in the meeting of the Pontifical Academy of Social Sciences on April 15 to mark the 25th anniversary of an encyclical by Pope John Paul II that addressed economic questions amid the fall of the Soviet Union.
Sanders had faced criticism for the Vatican trip, with some suggesting he had invited himself to the event for political purposes.
On Friday, Margaret Archer, president of the academy, called Sanders'participation a "monumental discourtesy" that would inject politics into a non-political gathering, Bloomberg News reported.
Sanders said in a statement that he was "delighted" to participate in the meeting on "restoring social justice and environmental sustainability to the world economy."
"I am a big, big fan of the pope," Sanders, who is Jewish, said in an interview on broadcaster MSNBC. "He has played an unbelievable role of injecting a moral consequence into the economy."
- DPA