"Chastity should be fertile, it generates spiritual children," he told 800 nuns from numerous religious orders. "Motherhood is sacred ... you must be mothers and not old maids."
Francis has emphasized the role of women in the church since he became pope in March, ANSA reported.
But he has also criticized U.S. nuns who have deviated from Catholic doctrine by promoting what he has referred to as radical feminist themes.
Boston schools pull out free condoms over wrapping complaints
NBC reportedly holds celebs hostage to Jimmy Fallon's show