President Donald Trump has said his plan to ban immigration into the US will last for 60 days and apply to those seeking permanent residence.
Speaking a day after he announced the move in an ambiguous tweet, Mr Trump said the measure would protect American jobs during the coronavirus crisis.
Farm labourers and hi-tech employees on special visas would not be affected.
Critics say he is trying to distract attention away from his response to the virus. The US has nearly 45,000 deaths.
Democrats also accuse the administration of using the pandemic to crack down on immigration. The issue has traditionally been a strong campaigning theme for Mr Trump, a Republican, but has taken a back seat during the crisis and in the lead-up to the November election.
At a White House coronavirus briefing, Mr Trump said the executive order with the decision was likely to be signed on Wednesday. The ban could be extended "much longer" depending on how the economy was doing, he said.
After vowing to suspend "all immigration to US" on Monday night, Mr Trump seemed to have changed his initial plan to include other immigrants after a reported backlash from some business leaders.
What did President Trump say?
More than 22 million Americans have lost their jobs amid the coronavirus outbreak, and the president said the government had a "solemn duty" to ensure they regain their jobs.
"It would be wrong and unjust for Americans laid off by the virus to be replaced with new immigrant labour flown in from abroad," he said, adding that there could be some exemptions.
"We want to protect our US workers and I think as we move forward we will become more and more protective of them".
Mr Trump's order could spark legal challenges.
The US has recorded more cases of coronavirus than anywhere else in the world at more than 820,000 cases, according to the Johns Hopkins University, which is tracking the disease globally.
What are green cards?
- They immigrants legal permanent residence and the opportunity to apply for American citizenship
- In a typical year, nearly one million green cards are issued in the US
- The majority – roughly 70% – go to those with relatives living in the US, according to a 2018 report from the US Senate
- For employment-based green cards, a coRead More – Source