The Trump administration has threatened to stop processing international flights in major cities around the country as a reaction to protests against immigration enforcement.

Markwayne Mullin, the homeland security secretary, said during an interview with Fox News on Tuesday that the administration is “drawing up plans” to take the action, in response to days of clashes at an Immigration and Customs Enforcement (ICE) detention center in New Jersey.

They plan to withdraw immigration processing services at cities with so-called sanctuary laws, which ban or limit local police from cooperating with federal immigration enforcement.

He questioned the provision of federal immigration services at Newark Liberty international airport while Democratic lawmakers were showing up and joining demonstrators in criticizing conditions inside the Delaney Hall ICE facility in Newark.

“If it belonged to us, we would take care of it, but it belongs to the city. And they’re barricading our employees from coming in and out of the [ICE] facility. Then why are we processing international flights into the airport there?” he said in the interview with Fox.

Customs and Border Protection (CBP) and the Transportation Security Administration (TSA) that provide security and immigration processing at airports are, along with ICE, part of the Department of Homeland Security (DHS).

For the last five days, hundreds of immigrants detained at the privately run Delaney Hall ICE detention facility in Newark have been engaged in a hunger and work strike, demanding improved conditions, medical care and for their immigration cases to move forward. Immigration officials violently clashed with protesters there on Tuesday evening, deploying pepper spray and Tasers.

The strike at the facility and clashes outside have escalated tensions between Democratic politicians opposing the facility and the Trump administration. On Monday, US senator Andy Kim was pepper-sprayed by ICE officers.

Mullin accused Kim and other Democratic politicians of “spreading smears” about ICE and engaging in political stunts. And on Tuesday evening, during an appearance on Fox News, Mullin threatened to end the processing of international flights in “sanctuary” cities.

“If they’re going to not allow us to go out and arrest the ‘worst of the worst’… then why are we processing international flights into the airport there?” Mullin asked in the Fox interview, adding that they are “currently drawing up plans to say: Listen, in these sanctuary cities, where the local radical left Democrats aren’t allowing us to do our job and enforce federal laws – then we shouldn’t be processing international flights into their cities, either.”

Sanctuary policies do not prevent ICE operations but rather limit some collaborations between local officials and the federal immigration enforcement agency.

On Wednesday, the hunger strike continued inside the Delaney Hall facility. Adriano Espaillat, a New York congressman, was able to enter the detention center for an oversight visit.

“The conditions, the food conditions are horrible. We feel that they’re not getting medical services. We feel that they’re overcrowded, and they’re denied their fundamental rights,” Espaillat said. “We will continue to fight to shut this place down.”