The Pope said in a message to a colloquium on migration and development taking place in Mexico that the humanitarian emergency requires "as a first urgent measure" that these children be "welcomed and protected."
But he stressed these measures will not be sufficient "unless they are accompanied by policies that inform people about the dangers of such a journey and, above all, that promote development in their countries of origin."
US authorities have detained some 57,000 unaccompanied minors since October, twice the number from the same period a year ago. Mexican authorities have picked up 8,000 child migrants in the first five months of the year, and more than half of them were traveling by themselves.
The immigrant children have been fleeing strife in Central America, while others are thought to be motivated by a desire to reunite with family in the US.
The Pope said the challenge "demands the attention of the entire international community so that new forms of legal and secure migration may be adopted."
He pointed out that migration is still widely seen as an emergency, but has actually now become "a hallmark of our society and a challenge."
Francis repeated that attitudes towards migrants must change, moving away from "defensiveness and fear, indifference and marginalization – all typical of a throwaway culture – towards attitudes based on a culture of encounter, the only culture capable of building a better, more just and fraternal world".
Addressing the Colloquium, Vatican Secretary of State Cardinal Pietro Parolin stated: "Whether they are traveling because of poverty, or violence, or with the hope of reuniting with relatives on the other side of the border, it is urgent to protect them and help them because their vulnerability is greater and they are defenseless against any abuse or misfortune”.