Democrats pushed back Wednesday against Homeland Security chief Kirstjen Nielsen, ripping her department for separating children from their families and for holding minors in what Mississippi Rep. Bennie Thompson called “cages.”

“Sir, we don’t use cages for children,” Nielsen shot back during a hearing before the House Homeland Security Committee, which Thompson chairs.

“In the border facilities that you’ve been to, they were not made to detain children. As the children are processed through, they are in some parts of those facilities. I’m being as clear as I can, sir,” she said.

“Yes or no, are we still putting children in cages?” Thompson, a Democrat, persisted.

“To my knowledge, CBP [Customs and Border Protection] never purposely put a child in a cage,” Nielsen said.

“I’ve seen the cages, I just want you to admit the cages exist,” Thompson declared.

“Sir, they’re not cages, they are areas of the border facility that are carved out for the safety and protection of those who remain there while they’re being processed,” she explained.

Rep. Bonnie Watson Coleman (D-NJ) also focused on the issue — and put Nielsen on the spot in a sharp back-and-forth.

“What is a chain-link fence enclosed into a chamber on a concrete floor? A cage?” she asked.

“It’s a detention space, ma’am,” Nielsen replied.

“Is it different from what you put dogs in?” the congresswoman countered.

“Yes,” Nielsen said.

“In what sense?” Coleman asked.

“It’s larger,” the Homeland Security chief continued.

“Sounds like a dog cage,” Coleman said.

Earlier, Nielsen warned lawmakers that the US needed to address what she called a “humanitarian catastrophe” on the Mexican border by supporting President Trump’s wall and cracking down on illegal migrants — even those seeking asylum.

“This is a crisis, pure and simple, and we need to respond accordingly,” Nielsen said.

Trump has prioritized border security and his long-promised wall on the southern border since he announced he was running for president.