Kristi Noem, President-elect Donald Trump's nominee to lead the Department of Homeland Security (DHS), vowed at her Senate confirmation hearing to lead a crackdown on immigration by securing the "war zone" at the US-Mexico border and deporting unauthorised migrants.

Noem's role as Homeland Security secretary is expected to be more limited in scope than her predecessors’, sources familiar with the Trump transition tell NBC News.

President-elect Donald Trump's choice for Homeland Security secretary portrayed illegal immigration as an "invasion" and the U.S.-Mexico border as a "war zone" during a U.S. Senate confirmation on Friday where she pledged to back Trump's hard line on immigration.