Tom Homan, President-elect Donald Trump’s new border czar, delivered a stern warning to sanctuary cities on Monday, telling them to “get the hell out of the way” as the new administration comes for illegal immigrants.

Mr. Homan was one of Mr. Trump’s boldest moves as he staffs his new administration. He also said he would nominate Rep. Elise Stefanik, a senior House Republican, to be America’s ambassador to the U.N. The incoming president also will name Stephen Miller to be deputy chief of staff for policy in the White House.

Mr. Miller was an architect of Mr. Trump’s immigration policy in his first term. Naming him and Mr. Homan marks an aggressive start to Mr. Trump’s attempts to fix the border.

Mr. Homan, in an interview with Fox News on Monday, laid out an expansive effort to carry out Mr. Trump’s mass deportation promises, saying the new administration will start with illegal immigrants who have criminal records or threaten national security. He also said the more than 1 million illegal immigrants already ordered deported but refusing to comply will be priority targets.

Mr. Homan aimed particular fury at sanctuary cities, saying they won’t be able to protect illegal immigrants from deportation.

“If sanctuary cities don’t want to help us, then get the hell out of the way. We’re coming,” he said.

Mr. Homan started his career as a Border Patrol agent, then served in U.S. Immigration and Customs Enforcement, eventually becoming acting director at the start of the Trump administration. He had been nominated to hold the position in full but met resistance in the Senate, where he never saw a confirmation vote.

He has spent the intervening years advocating for stiffer enforcement and criticizing President Biden.

Mr. Trump said he was eager to get Mr. Homan back to work.

“I’ve known Tom for a long time, and there is nobody better at policing and controlling our Borders. Likewise, Tom Homan will be in charge of all Deportation of Illegal Aliens back to their Country of Origin,” Mr. Trump said in announcing the pick on social media.

Vice President J.D. Vance confirmed Mr. Miller’s selection on social media.

Mr. Miller was a senior advisor to Mr. Trump during the first term, serving as as an architect of what became the calmest border in decades. Mr. Miller also was involved in the attempt to jail parents who jumped the border with children in 2018, which led to the migrant-family separations that marred Mr. Trump’s first term.

Mr. Trump also said this weekend that he will nominate Ms. Stefanik, the No. 4 Republican in the House, to become the U.S. ambassador to the U.N.

Ms. Stefanik had become one of the more outspoken defenders of Mr. Trump and he, in comments announcing her nomination to the New York Post, praised her as “an incredibly strong, tough and smart America First fighter.”

She would require Senate confirmation. Mr. Homan would not, because “border czar” is not a formal position within the federal government.

The role will likely mean Mr. Homan serves as the president’s senior advisor on the issue, with authority to coordinate policy among various agencies and to see that the president’s wishes are carried out.

In the Biden administration, Vice President Kamala Harris was dubbed the border czar by news media and Washington politicians after Mr. Biden in 2021 gave her the job of trying to slow down the number of migrants leaving Central America. She resisted the czar label and avoided visiting the U.S.-Mexico border from summer 2021 until deep into this year’s presidential campaign.

On Monday, Mr. Homan told Fox News that he felt he had to step up after complaining about the Biden administration.

“I would be a hypocrite if I didn’t,” he said.

Mr Homan said his phone has been inundated with inquiries from former Border Patrol agents and ICE employees excited about his return.

But he said he’s also gotten “death threats rolling in.”

Mr. Trump has signaled he wants to see mass deportations, though what that looks like in practice is still being developed.

Mr. Homan said the top priority will be “public safety threats and national security threats.”

He also said illegal immigrants who are defying deportation orders will be targeted. There are an estimated 1.1 million people in that category.

And Mr. Homan vowed to tackle the drug and migrant-smuggling cartels that have turned the border chaos into a multi-billion dollar industry.

“The criminal cartels are going to be put out of business by this president,” Mr. Homan said.

• Alex Swoyer and Mallory Wilson contributed to this report.

• Stephen Dinan can be reached at sdinan@washingtontimes.com.