"They have to know when they come up, they can't get in or it's never gonna stop," Trump said at the White House Tuesday while speaking with the National Federation of Independent Businesses.
"We have to stop them coming in — politically correct or not — we have to have borders," he added.
President Trump is facing mounting anger as images have emerged of where the children are being kept, along with a heartbreaking audio clip of children pleading for their parents.
In one such clip, leaked to ProPublica, a weeping child can be heard crying out, "Papa! Papa!"
Lawmakers on both sides of the aisle have condemned the practice, including both Republican senators from Texas, Ted Cruz and John Cornyn.
The president's own wife, Melania Trump, released a statement via her spokeswoman saying she "hates to see" children separated from their families.
"She believes we need to be a country that follows all laws, but also a country that governs with heart," Stephanie Grisham, the first lady’s spokeswoman, said in the statement.
On "The View," Meghan McCain challenged the president's daughter Ivanka Trump to intervene.
"Where is Ivanka Trump?" she asked. "That's what I want to know."
But some anchors have a different take. Fox's Laura Ingraham received some criticism for comparing the controversial detention centers to summer camps.