He told CBS News: "When you're apprehended on the street or at a factory, it's obviously not easy to establish with evidence that you've been here for more than two years because you're not carrying all your doc.u.ments with you."

Who is objecting?

Within hours of the policy being announced on Monday, the ACLU said that it was planning to launch a legal challenge.

"We are suing to quickly stop Trump's efforts to ma.s.sively expand the expedited removal of immigrants," the rights group tweeted.

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"Immigrants that have lived here for years will have less due process rights than people get in traffic court. The plan is unlawful. Period."

Vanita Gupta, president of the Leaders.h.i.+p Conference on Civil and Human Rights, told reporters: "The Trump administration is moving forward into converting ICE [Immigration and Customs Enforcement] into a 'show me your papers' army."

Legal expert Jackie Stevens, a political science professor at Northwestern University, told Reuters that about 1% of the people detained by ICE and 0.5% of those deported were actually US citizens.

"Expedited removal orders are going to make this much worse," she said.

Hundreds of thousands of people have taken to the streets in Puerto Rico to demand the resignation of the island's embattled governor, Ricardo Rosselló.

It comes a day after Mr Rosselló said he would not step down over a leaked online chat in which he and top aides exchanged obscenity-laced messages.

He said he would leave office next year, at the end of his term.

But protesters have said he must stand down immediately and the number of marchers on the streets has increased.

Why are there protests in Puerto Rico?

Bad Bunny stops tour to protest in Puerto Rico

The leaked text messages included h.o.m.ophobic slurs as well as insults about victims of the deadly Hurricane Maria in 2017.

Asked about the matter, US President Donald Trump said Mr Rosselló was "a terrible governor".

"You have totally grossly incompetent leaders.h.i.+p at the top of Puerto Rico," he told reporters at the White House. "The leaders.h.i.+p is corrupt and incompetent."

Footage early on Monday morning showed crowded trains headed to the capital, and long lines of protesters preparing to march in the sweltering Caribbean heat.

Some protesters were seen blocking highways while chanting "Ricky resign". The hashtags #RickyRenuncia ("Ricky resign") and #ParoNacional (national strike) both trended on Twitter.

Experts predicted the crowd size would eclipse the largest protest in the island's history 15 years ago, when Puerto Ricans successfully pet.i.tioned the US military to end training missions on the island of Vieques.