President-elect Donald J. Trump said late Sunday that he had named Thomas D. Homan, a senior immigration official in his last administration, as the “border czar” in charge of the nation’s borders and its maritime and aviation security.

Mr. Trump made the announcement in a brief post on his social media platform, Truth Social, that did not provide other details on Mr. Homan’s new job.

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

Mr. Trump made a broad crackdown on immigration a pillar of his presidential campaign, but it is so far unclear what that would look like or what his presidency will mean for immigrants in the United States.

One major question is whether the new administration will implement large-scale worksite raids that could lead to the arrest of unauthorized workers. Mr. Homan said on CBS’s “60 Minutes” last month that such raids, which have not been conducted under President Biden, would resume under the new administration. Mr. Trump takes office on Jan. 20.

Mr. Homan was named acting director of Immigration and Customs Enforcement in 2017, and he has decades of experience in immigration enforcement. He was a police officer, a United States Border Patrol agent and a special agent with the former Immigration and Naturalization Service.

Mr. Trump’s announcement on Sunday was the latest clue into who will — and won’t — be his cabinet members and closest advisers. On Thursday, Mr. Trump named Susie Wiles, who has run his political operation, as his White House chief of staff. On Saturday he said that he would not invite Nikki Haley, his former ambassador to the United Nations, or Mike Pompeo, his former secretary of state, to join the new administration.