Donald Trump has used emergency powers to deny asylum to immigrants who enter the US illegally as caravans of Central Americans march towards their borders.
The President invoked powers tightening security at the border with Mexico this afternoon before flying off to Paris to meet world leaders at commemorations for the centenary of the First World War.
The order he signed will mean thousands of migrants, most of whom are travelling on foot, will not be able to seek asylum in the US for the next 90 days at least.
The proclamation signed by Trump, said the US expected the arrival "of a substantial number of aliens", and is likely to be challenged in court.
He announced the signing of the document with a tweet linking to the full terms of his proclamation.
He used the same powers which helped him push through a version of the travel ban that was upheld by the Supreme Court - this time circumventing US laws stating that anyone is eligible for asylum no matter how they enter the country.
As the order was passed with effect from tomorrow, thousands of migrants departed from Mexico City on their way to the northern city of Tijuana, opting for the longer but safer route to the US.
"We need people in our country but they have to come in legally and they have to have merit," Mr Trump said.
He tweeted the proclamation at 3pm GMT (7am Washington), and has already attracted a whirlwind of criticism from users, with some branding the order "Republiporn".
But the busy ports of entry already have long queues, forcing immigration officials to tell some migrants to turn around and come back to make their claims.
The proclamation said the US expected the arrival "of a substantial number of aliens... who appear to have no lawful basis for admission into our country"
"Many entered Mexico unlawfully — some with violence — and have rejected opportunities to apply for asylum and benefits in Mexico," said the White House, also warning that the mass migration: "Will contribute to the overloading of our immigration and asylum system and to the release of thousands of aliens into the interior of the United States."
According to the White House, an average of 2,000 "inadmissible aliens" have entered the states each day from the south, and 124,511 over 2018. Another 396,579 were apprehended.
It is not known whether those in the caravan, many fleeing violence in their homeland, plan to cross illegally. It is believed most were pushed by political instability and rising poverty.
Administration officials said those denied asylum under the proclamation may be eligible for similar forms of protection if they fear returning to their countries, though they would be subject to a tougher threshold.
Those forms of protection include "withholding of removal" - which is similar to asylum, but does not allow for green cards or bringing families - or asylum under the United Nations Convention Against Torture.
During yesterday's heated argument in Washington which saw CNN reporter Jim Acosta ousted from White House press corps, Mr Trump said he "considers it an invasion".
He denied demonising immigrants. I want them to come into the country but they have to come in legally. We need the people."
He admitted using campaign images which showed migrants climbing over walls, but said "It's true. They're not actors, they didn't come from Hollywood."
The announcement today punctuated Mr Trump's hardline stance on immigration through regulatory changes and presidential orders, bypassing Congress.
Those efforts have been largely thwarted by legal challenges and, in the case of family separations this year, stymied by a global outcry that prompted him to scrap them.
The new changes are likely to be met with legal challenges too. Omar Jadwat, director of the American Civil Liberties Union's Immigrants' Rights Project, said they were clearly illegal.
"US law specifically allows individuals to apply for asylum whether or not they are at a port of entry. It is illegal to circumvent that by agency or presidential decree," he said.
Curbing immigration has been a signature issue for Mr Trump, who pushed it hard in the days leading up to Tuesday's midterm elections, railing against the caravans that are still hundreds of miles from the border.
He has made little mention of the issue since the election but has sent troops to the border in response.
On Thursday, there were more than 5,600 US troops deployed to the border mission, with about 550 actually working on the border in Texas.
The military is expected to have the vast majority of the more than 7,000 troops planned for the mission deployed by Monday, and that number could grow.
