According to Reuters, Francis, who turned 78 on Wednesday, improvised the comment at the end of an address to members of Italy's national Olympic committee.
After offering "best wishes for your candidacy," the pope, an avid football fan, paused, smiled and added: "But I won't be here," bringing laughter to the group in a Vatican hall.
Italian media have reported that Olympic organisers want to hold some events, such as archery or badminton, in St. Peter's Square, which borders with Rome but is on Vatican territory. The Vatican has said it would consider requests.
In August, the pope, who appears to be in good health, told reporters that he expected "to return to the house of the father" (God) in two or three years.
He has also said he would not hesitate to resign for health reasons, as did his predecessor, former pope Benedict XVI. But aides have said he would probably go to a convent in his native Argentina rather than stay in the Vatican as Benedict did.
