Vatican City - Pope Francis made a foray into the US election season with a rare television interview Sunday, calling harsh anti-migrant attitudes "madness" and criticizing right-wing US Catholic figures for overly conservative stances against his social teachings.

Speaking in his native Spanish through a translator for more than an hour, Francis told CBS News' 60 Minutes that the closing by the state of Texas of a Catholic charity offering humanitarian assistance was absurd.

"That is madness. Sheer madness. To close the border and leave them there, that is madness. The migrant has to be received," the pope said.

"Thereafter you see how you are going to deal with him. Maybe you have to send him back, I don't know, but each case ought to be considered humanely," Francis said.

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Record numbers of migrants have been seeking to enter the United States, largely from Central America and Venezuela, as they flee poverty, violence, and disasters exacerbated by climate change and a legacy of US interventionism.

The matter has emerged as a top political issue in the November election as President Joe Biden faces a looming rematch with Republican challenger Donald Trump.

"The globalization of indifference" on migrants, Francis said, "is a very ugly disease."

Francis (87) also addressed criticisms by conservative US bishops who oppose his efforts to revisit certain teachings and traditions.

A "conservative is one who clings to something and does not want to see beyond that," he said when asked about the bishops, adding "it is a suicidal attitude."

Since his election in 2013, Pope Francis has insisted on the importance of a church open to all, including members of the LGBTQ+ community, but he has faced strong resistance from conservative Catholics.

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There was a particularly strong reaction when Francis opened the door to the blessing of gay couples last year.

Calling gay people "a human fact," Francis said in the interview: "To bless each person, why not? The blessing is for all."

The pontiff also touched on the controversial topic of sex abuse within the Catholic Church.

He has made combatting sexual assault in the Church one of the main missions of his papacy, and insisted on a "zero tolerance" policy following multiple wide-reaching scandals.

"Unfortunately, the tragedy of the abuses is enormous," he told CBS, adding that abuse "cannot be tolerated."

"When there is a case of a religious man or woman who abuses, the full force of the law falls upon them," Francis said.

But, he added, "there has been a great deal of progress."