The government said "expedited removal" by stripping court oversight would free up detention space and ease strains on immigration courts, which face a backlog of more than 900,000 cases.
The Trump administration said on Monday that it would expand and speed up the deportation of migrants who enter the US illegally by stripping away court oversight, enabling officials to remove people in days rather than months or years.
Set to be published in the Federal Register on Tuesday, the rule will apply "expedited removal" to the majority of those who enter the US illegally unless they can prove they have been living in the country for at least two years.
No attorney access
Legal experts said it was a dramatic expansion of a programme already used along the US-Mexican border that cuts out review by an immigration judge, usually without access to an attorney. Both are available in regular proceedings.
"The Trump administration is moving forward into converting ICE (Immigrations and Customs Enforcement) into a 'show me your papers' army," said Vanita Gupta, the president of The Leadership Conference on Civil and Human Rights, on a call with reporters.
It was likely the policy would be blocked quickly by a court, several experts said. The American Civil Liberties Union, which has filed suit to block numerous Trump immigration policies in court, has vowed to sue.
President Donald Trump has struggled to stem an increase of mostly Central American families arriving at the US-Mexico border, leading to overcrowded detention facilities and a political battle over a growing humanitarian crisis.
The government said increasing rapid deportations would free up detention space and ease strains on immigration courts, which face a backlog of more than 900,000 cases.
Nearly 300,000 of the approximately 11 million immigrants in the US illegally could be quickly deported under the new rule, according to the non-partisan Migration Policy Institute.
Erosion of due process?
The Department of Homeland Security (DHS) said 37 percent, or 20,570 of those encountered by ICE in the year to September, had been in the country less than two years.
People in rapid deportation proceedings are detained for 11.4 days on average, according to DHS.
People in regular proceedings are held for 51.5 days and are released into the US for the months or years it takes to resolve their cases.
Legal experts said the rule shreds basic due process and could create havoc beyond immigrant communities.
"ICE has been detaining and deporting US citizens for decades," said Jackie Stevens, a political science professor at Northwestern University.
That policy came at a great cost to US taxpayers in terms of litigation and compensation, she added.
US citizens account for about 1 percent of those detained by ICE and about 0.5 percent of those deported, according to Stevens' research.
"Expedited removal orders are going to make this much worse," she said.
The US Court of Appeals for the 9th Circuit in San Francisco in March ruled that those ordered deported in the sped-up process have a right to take their case to a judge.
Previously, only those immigrants caught within 100 miles of the border who had been in the country two weeks or less could be ordered rapidly deported. The policy makes an exception for immigrants who can establish a "credible fear" of persecution in their home country.