Pope Francis has suggested that there could be ways for the Catholic Church to bless same-sex unions.
The letter suggests blessings could be used if they were not confused with sacramental marriage.
Francis said priests cannot become judges “who only deny, reject and exclude”.
He added that blessing gay unions should not become an official rule but should be decided case by case.
Catholic priests in northern European countries have for years blessed same-sex couples, in defiance of the Vatican ban.
The Pope said blessings should apply even in situations “that from an objective point of view aren’t morally acceptable”.
The Pope’s shift on gay unions comes before a key synod of bishops, which starts this week at the Vatican and will tackle contentious issues including homosexuality, the introduction of female deacons and married priests.
The Catholic Church officially considers homosexual sex “intrinsically disordered” and the Pope has long opposed gay marriage, maintaining that wedlock can be only between a man and woman.
Francis has supported same-sex civil unions, however, arguing that gay couples need legal rights, and told a gay man in 2018: “God made you that way and loves you as you are.”
Despite his stance, the Vatican’s doctrinal department said in 2021 that the church could not bless gay unions because “God cannot bless sin”.