The Trump administration is launching a new effort to keep immigrants who entered the U.S. illegally detained by denying them bond hearings, an internal memo showed, a change that could further swell the numbers of those held.

The guidance by the U.S. Immigration and Customs Enforcement, a portion of which Reuters reviewed, could be applied to millions of people who crossed the border illegally and are contesting their deportation.

President Donald Trump has vowed mass deportations, which he says are needed after high levels of illegal immigration under his predecessor, Democrat Joe Biden.

Congress passed a spending law this month that provides funding to detain at least 100,000 people, a steep increase over the record 58,000 in custody by late June.

The Washington Post first reported, opens new tab the new ICE policy limiting bond hearing eligibility, citing a July 8 memo by its acting director, Todd Lyons.

The guidance shared with Reuters called for ICE to interpret several immigration law provisions as "prohibitions on release" after an arrest, adding the shift in policy was "likely to be litigated."

It encouraged ICE prosecutors "to make alternative arguments in support of continued detention" during immigration court hearings.

The new policy appeared to reverse legal standards governing detention for decades, said Tom Jawetz, a former homeland security official in the Biden administration, calling it "a radical departure that could explode the detention population."

The U.S. Department of Homeland Security and ICE did not immediately respond to requests for comment.