US President-elect Donald J Trump is signaling with his staffing decisions his intention to carry out a campaign promise of widespread deportations of undocumented immigrants and tightening of measures that allow some of them to stay in the country legally.

Stephen Miller, an immigration hardliner and adviser to Trump, is taking over policy planning for the transition and is expected to be named deputy chief of staff in his administration, people briefed on the matter said on Monday.

And late on Sunday, Trump announced on social media that Thomas Homan, the acting director of the Immigration and Customs Enforcement agency during Trump's first term, would be his "border czar."

It remains to be seen how broad Miller's portfolio will be, but it is expected to be vast and to far exceed what the eventual title will convey, according to the people briefed on the matter. A Trump spokesman did not immediately respond to a request for comment. Miller also did not respond to a message seeking comment. Miller's views are favored by Trump's hard-line base. Vice President-elect JD Vance and Donald Trump Jr., who has been influential in the transition, praised the prospective choice on X.