Pope Francis added to his reputation for being an open-minded pope when he said Monday that the centuries-old tradition of celibacy could be altered, Reuters reported.

Francis said while he prefers that Roman Catholic priests remain celibate, "the door is always open to change," when it comes to altering the rule.

"Celibacy is not a dogma," Francis replied when asked if the Catholic Church would ever allow priests to marry, according to Reuters.

The pope's comments comes at a time the Church is facing widespread criticism and pressure from the United Nations to check the rampant sexual abuse allegedly covered up by church officials.

The pope made the comments on a plane while returning from a trip to the Middle East. He has expressed similar opinions in the past when he was archbishop of Buenos Aires, but this is the first time he did so as pope.

"[Celibacy] is a rule of life that I appreciated very much and I think it is a gift for the Church but since it is not a dogma, the door is always open."

Other sects within Christianity, including the Anglican and Protestant church, allow priests to marry.

The practice of Catholic priests being celibate, which dates back to 1,000 years, stems from the belief that a priest should completely immerse himself into the Church. In other words, the Church becomes a spouse, Reuters reported.

But the tradition is not a dogma, meaning a Church rule that cannot be altered. An alternative is optional celibacy, which supporters say could prevent child abuse that's most likely caused by sexually frustrated priests.

The Church says those who sexually abuse children are pedophiles, which comes from psychological problems, Reuters reported.

Francis, who in 2013 was Time's Person of the Year, said last summer that he will not "judge" homosexuals. He also called on women to take more responsibility in the Church.