Pope Francis has decried the "inhuman" conditions facing migrants crossing the U.S.-Mexico border and has encouraged frontier communities to not judge people by stereotypes but rather welcome migrants and work to end discrimination.

Francis made the appeal in a letter to a Jesuit priest who helps organize Catholic teens in Nogales, Arizona, to support the Kino Border Initiative, which advocates a more humane solution to migration.

He wrote: "These young people — who have come to learn how to strive against the propagation of stereotypes, from people who only see in immigration a source of illegality, social conflict and violence — can contribute much to show the world a church without borders, as mother of all."

Francis will likely raise immigration issues when he visits the U.S. in September.