The US government is introducing a new fast-track deportation process that will bypass immigration courts.
Under the new rules, migrants who cannot prove they have been in the US continuously for more than two years can be immediately deported.
Until now, expedited deportations could only be applied to those detained near the border who had been in the US for less than two weeks.
Rights groups say hundreds of thousands of people could be affected.
The American Civil Liberties Union (ACLU) says it will challenge the policy in court.
The new rule is expected to be implemented with immediate effect after it is published on Tuesday.
US immigration policy has come under increasing scrutiny in recent months - in particular, the conditions at the country’s detention centres on the southern border with Mexico.
Kevin McAleenan, acting secretary of Homeland Security, said the change would “help to alleviate some of the burden and capacity issues” at the border.
He added that it was “a necessary response to the ongoing immigration crisis”.
Analysts say US President Donald Trump is planning to make hardline immigration control a key element of his re-election campaign in 2020. BBC