Pope Francis has condemned U.S. President Donald Trump’s deportation of undocumented migrants, warning that such actions threaten human dignity and leave vulnerable people defenseless.

In a letter to U.S. bishops on Monday, the pope urged the clergy to resist narratives that discriminate against migrants and cause unnecessary suffering.

He emphasized the importance of welcoming, protecting, and integrating those fleeing conflicts, poverty, and climate disasters—within reasonable capacity limits.

“This does not impede the development of a policy that regulates orderly and legal migration. However, this development cannot come about through the privilege of some and the sacrifice of others. What is built on the basis of force, and not on the truth about the equal dignity of every human being, begins badly and will end badly.” The Pope added.

Trump, who has been in office for just a month, has launched a series of executive actions targeting undocumented immigrants. These measures include changes to migrant repatriations, border control, and policies concerning refugees and asylum seekers, with Trump promising “mass deportations.”

He has suggested deporting between 15 and 20 million people—ten times the number deported during his first term and more than the estimated 11 million undocumented migrants currently in the country.