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.

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."