VATICAN CITY - Pope Francis has lamented that children, as he puts it, are being taught at school that gender can be a choice.

Francis said: "Today, in schools they are teaching this to children -- to children! -- that everyone can choose their gender."

Without specifying, he blamed this on textbooks supplied by "persons and institutions who donate money."

Francis weighed in during a closed-door meeting last week with bishops from Poland during his pilgrimage there. The Vatican released a transcript Tuesday of those private remarks.

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The pope blamed what he called "ideological colonizing" backed by "very influential countries" which he didn't identify.

One such "colonization" he said -- "I'll say it clearly with its first and last name -- is gender."

The pontiff has during his reign displayed unusually progressive views for the leader of the Catholic Church.

In a 260-page document titled "The Joy of Love" released in April, he expressed views that seemed to understand the pressures of modern families and relationships.

Francis famously said, "Who am I to judge?" when once asked about homosexuals, however he as ruled out same-sex marriages.

He calls divorce evil, but he has left the door open for people who are remarried without an annulment to take communion.

On gender identity, "The Joy of Love" affirmed the church's opposition to gender switching, saying it is necessary to accept our humanity "as it was created."