Donald Trump has vowed to suspend all immigration into America in response to the coronavirus crisis, but provided few details about the move, leading to widespread confusion.
The US president cited both the Covid-19 pandemic and the need to protect American jobs in a 38-word tweet making the announcement.
He wrote: "In light of the attack from the Invisible Enemy, as well as the need to protect the jobs of our GREAT American Citizens, I will be signing an Executive Order to temporarily suspend immigration into the United States!"
Yesterday, his officials were scrambling to explain the policy declared in the tweet, with no press release or detailed explanation being issued in public.
Taken at face value, the tweet suggests Mr Trump plans to temporarily halt the issue of visas for immigrants and green cards, which are permits allowing foreigners - often with US family members - to live in America permanently.
Such a move would affect huge numbers of people. About 460,000 immigration visas were issued last year and around 580,000 green cards.
Some exemptions could be given, with US officials reportedly indicating that health workers and farmers would be exempt given demand during the pandemic.
Irish people hoping to secure visas to work or study in America could be affected, though given the sparsity in the policy's details there is little clarity.
It is unclear what will happen to applications already filed, though in reality the process had already largely ground to a halt with the State Department suspending routine visa services.
The move would break with historical precedent. America continued to accept immigrants during both the Spanish flu of 1918 and the Second World War. It also underscores Mr Trump's "America First" vision. The US president has repeatedly said that the coronavirus crisis has shown the importance of national borders.
Mr Trump's move focuses on legal immigration. He has already moved to curb illegal immigration during the pandemic, ordering the immediate deportation of those caught crossing the border without paperwork, including asylum seekers.
The legal basis for Mr Trump's executive order, which officials were working on yesterday, was initially unclear. He could halt immigration for health concerns, citing the pandemic.
The suspension is likely to be temporary. It is also likely to be challenged through the courts, as many of Mr Trump's most notable immigration policies have been. However, Democrats and immigrant rights' bodies criticised the move, accusing the president of exploiting the crisis.
America has recorded around 780,000 Covid-19 cases, with more than 42,000 people dying from the virus.
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