Former Immigration Customs Enforcement (ICE) director Tom Homan said in an interview that aired Wednesday on "Rising" that sanctuary cities are the biggest factor impeding deportations in the U.S.

"Sanctuary cities [are] the biggest effect because one officer can sit in county jail and process 12 illegal aliens a day," Homan, who served under President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE, told Hill.TV hosts Krystal Ball and Buck Sexton earlier this week.

"We used to have full presence in Los Angeles County Jail. We used to have full presence at Rikers Island," he continued. "New York City, the site of the most horrific terrorist attacks this country ever saw, at the hands of some that were in the country illegally."

"So we lost any efficiency because one agent can sit there and process 12 illegal aliens in jail in a shift, but when that jail no longer works for you, they're going to release that person back into the community," he said, referring to officials in sanctuary cities who do not cooperate with federal immigration authorities.

"Now you've got to send a whole team. First to locate them, people that don't want to be found, you've got to find them. Two, once you find them, it takes a lot of resources to arrest them," he said.

"Again, it's an administrative process, so it takes a lot of planning," he said. "It slows us down."

Reports surfaced earlier this month that President Trump is interested in sending immigrants apprehended at the border to the sanctuary cities in an effort to punish Democrats for their immigration policies.

The Trump administration has also been embroiled in legal battles over the municipalities.

A panel of federal judges earlier this month denied the Trump administration's request to block California from carrying out some "sanctuary city" laws that would protect certain immigrants without legal status in the state.

— Julia Manchester