NEW YORK — President-elect Donald Trump is naming longtime adviser Stephen Miller, an immigration hard-liner, to be the deputy chief of policy in his new administration.

Later on Monday, Trump added another loyal supporter to his future administration, naming former New York Rep. Lee Zeldin to lead the Environmental Protection Agency.

Miller is one of Trump’s longest-serving aides, dating back to his first campaign for the White House. He was a senior adviser in Trump’s first term and has been a central figure in many of his policy decisions, particularly on immigration, including Trump’s move to separate thousands of immigrant families as a deterrence program in 2018.

Miller has also helped craft many of Trump’s hard-line speeches and was often the public face of those policies during Trump’s first term in office and during his campaigns.

In a statement, Trump said that Zeldin, a Republican who mounted a failed bid for governor of New York in 2022, will “ensure fair and swift deregulatory decisions that will be enacted in a way to unleash the power of American businesses.’’

Zeldin also will maintain “the highest environmental standards, including the cleanest air and water on the planet,’’ Trump said.

Trump’s statement misidentified the name of the agency Zeldin was picked to lead, labeling it the Environmental Protective Agency.

Zeldin, who left Congress in January 2023, was a surprising pick for the role. His public appearances both in his own campaigns and on behalf of Trump often had him speaking about issues such as the military, national security, antisemitism, U.S.-Israel relations, immigration and crime.

He was among the Republicans in Congress who voted against certifying the 2020 election results. While in Congress, he did not serve on committees with oversight of environmental policy and had a lifetime score of 14% from the League of Conservation Voters during his eight years in Congress.

Because it is a Cabinet position, Zeldin’s appointment requires Senate confirmation.