Lisbon, Portugal - Pope Francis lamented the "strong reactionary attitude" of some Catholics in the US who refuse to embrace change in the Church, in comments published Monday.

During World Youth Day on August 5, the 86-year-old pontiff made some comments causing a stir, only recently made public by Civilta Cattolica magazine, while speaking to Jesuits.

One Jesuit asked about criticism of the pope's leadership by some senior American Catholics, many of whom complain Francis is not outspoken enough on abortion, and too compassionate towards homosexuals and divorced adults.

"You have seen that in the United States the situation is not easy: there is a very strong reactionary attitude," Francis replied.

"I would like to remind those people that 'indietrismo' [which means to be backward-looking] is useless, and we need to understand that there is an appropriate evolution in the understanding of matters of faith and morals," he explained.

Citing slavery as an example, he said "some pontiffs before me tolerated it, but things are different today."

"When you go backward, you form something closed, disconnected from the roots of the Church and you lose the sap of revelation," he continued, adding that "you can lose the true tradition, and turn to ideologies for support."

"It takes a lot of sensitivity and creativity to accompany people spiritually," he added. "But everyone, everyone, everyone is called to live in the Church. Never forget that."