Department of Homeland Security (DHS) Secretary Markwayne Mullin raised the possibility of restricting customs privileges at airports in sanctuary cities during an appearance on "Special Report" Monday.

In his first interview as secretary, Mullin told Fox News that DHS will be taking a closer look at customs enforcement operations at major international airports located in sanctuary jurisdictions, questioning their efficacy.

"If they're a sanctuary city, should they really be processing customs into their city?" Mullin asked.

"If they're a sanctuary city and they're receiving international flights, and we're asking them to partner with us at the airport, but once they walk out of the airport, they're not going to enforce immigration policy — maybe we need to have a really hard look at that."

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Los Angeles International Airport (LAX) and John F. Kennedy International Airport (JFK) are examples of major customs hubs that DHS could be looking into, as both are located in sanctuary cities. According to Port Authority, roughly 3 million people pass through customs each month at JFK.

"I'm going to have to be forced to make hard decisions," Mullin said. "I am not going outside the policies that Congress passed for me, and we're not trying to push those, but we're saying you've got to partner with us."

Mullin also warned that sanctuary cities more broadly may be at risk under his leadership of DHS, claiming they are unlawful.

"I believe sanctuary cities, it’s not lawful," he told Fox News chief political anchor Bret Baier. "I don't think they're able to do that. And so, we're going to take a hard look at this."

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Mullin took the helm of DHS after his predecessor, Kristi Noem, was fired by President Donald Trump March 5, after she carried out Trump’s mass-deportation agenda for more than a year.

Trump was reportedly "furious" with Noem saying during a Senate hearing that he knew about a taxpayer-funded ad contract. The White House told Fox News Digital Trump did not know about the contract.

Mullin shared his plans for leading the department that has become embattled with controversy.

"My job is to empower them [employees] to do their jobs," he explained. "How do I make sure that they have the tools and the assets they need and the manpower they need to be able to go out and deliver the mission that Congress and the president has tasked us with?"

During his confirmation hearing, Mullin said one goal is that within six months, he hopes DHS will not be in the headlines every day.

"Right now, we get more correspondence from media than the White House does," Mullin revealed.

"It’s become such a political hotbed. And really, why is Department of Homeland such a political hotbed? All they're doing is trying to keep our streets safe, trying to keep our nation secure, trying to keep bad actors from having terrorist attacks on the homeland. It should be something we all get behind," he added.

Mullin also spoke about the ongoing partial government shutdown as Congress fails to agree on a funding plan for DHS. He accused Democrats of putting the country in a vulnerable state amid conflict with Iran.

"It’s putting our mission at risk," he said. "We have some very challenging times right now."

"How we get past this is that we've got to put the partisan bickering aside and say, 'What's best for America? What's best for moving forward?'"