Pope Francis issued a fierce rebuke of President Donald Trump’s mass deportation efforts on Tuesday, calling it a “major crisis” in the U.S. and warning that it “will end badly.”

In a letter to U.S. bishops, the pope criticized the criminalization of migrants based on their legal status and the sweeping deportations of those fleeing hardship, saying it “damages the dignity of many men and women, and of entire families, and places them in a state of particular vulnerability and defenselessness.”

“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,” he warned.

Pope Francis does not name Trump in his letter, but it is a clear directive to resist the demonization of migrants and refugees.

“I exhort all the faithful of the Catholic Church, and all men and women of good will, not to give in to narratives that discriminate against and cause unnecessary suffering to our migrant and refugee brothers and sisters,” he wrote.

In response to the pope’s criticism, Tom Homan, the Trump administration official overseeing immigration and border security, went on the offensive during an appearance on conservative news outlet Newsmax on Tuesday.

“Concentrate on the Catholic Church,” Homan, a Catholic, said in his on-air message to the pope. “You’ve got a lot of problems right there in the Catholic Church. You have enough to fix in your own home. Leave the border stuff to us. We know what we’re doing.”

The pope has been highly critical of Trump’s anti-immigrant efforts, going all the way back to the Republican’s first run for president in 2016. At the time, Pope Francis said Trump, whose campaign platform was centered on building a wall along the U.S.-Mexico border to keep migrants out, was “not Christian.”

Trump responded that if ISIS attacked the Vatican, the pope “would have only wished and prayed” that Trump was president “because this would not have happened.” He also called Pope Francis “a very political person.”

Last month, just ahead of Trump’s inauguration, the pope called Trump’s mass deportation proposal a “disgrace.”

“If it is true, it will be a disgrace, because it makes the poor wretches who have nothing to pay the unpaid bill,” he said when asked about Trump’s plans in an Italian TV interview. “It won’t do. This is not the way to solve things.”