Aboard the papal plane (CNN) If US President Donald Trump considers himself "pro-life," he should reconsider his decision to end a program that allows the children of undocumented immigrants to remain in the United States, Pope Francis said.

"The President of the United States presents himself as pro-life and if he is a good pro-lifer, he understands that family is the cradle of life and its unity must be protected," Francis said.

The Pope's comments came during a news conference Sunday aboard the papal plane, as he returned to the Vatican after a five-day trip to Colombia. In the wide-ranging Q&A with reporters, the Pope also said history will harshly judge deniers of climate change.

The Pope acknowledged that he was not familiar with the specifics of DACA. "I think this law comes not from parliament but from the executive," the Pope said. "If that is so, I am hopeful that it will be re-thought."

Trump and the Pope have tussled over immigration before , with the Pope saying last year that anyone who thinks only of building walls instead of bridges is "not Christian."

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