Washington DC - President Donald Trump talked up Thursday a self-deportation campaign that encourages undocumented migrants to voluntarily leave so they can come back legally at some point in the future.

"It's a very big self-deport operation that we are starting," Trump told a televised cabinet meeting.

"And we are going to work with people so that if they go out in a nice way, go back to their country, we are going to work with them right from the beginning on trying to get them back in legally," he added.

On his first day in power back in January, Trump deactivated an app introduced by his predecessor, Joe Biden, allowing migrants in Mexico to make appointments at US ports of entry and ask for temporary residency.

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It was a central part of Biden's strategy to ease pressure at the US-Mexico border by setting up temporary legal entry pathways under an authority called temporary parole.

This app, called CBP One, was used by hundreds of thousands of people to enter the US.

Now the Department of Homeland Security has created another app called CBP Home for those people to deport themselves and is notifying them they must leave right away.

Speaking at the televised Cabinet meeting, Homeland Security Secretary Kristi Noem said the government is working with authorities in El Salvador, Colombia, and Mexico to provide support to people who self-deport as they try to come back.

"So when they get there, they'll have housing and food assistance, and so making sure that these folks have the opportunity to go home, so that they can have the chance to come back to America, it's important," she went on, adding that thousands of people have already self-deported.

The Trump administration touts its sweeping drive against migrants – a key campaign promise – as being in part a crackdown on gang members and other violent criminals.

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At the same time, Trump said Thursday that his administration will work with farmers to allow some migrants to continue working, at least temporarily.

"We have to take care of our farmers and hotels and various places," Trump added.