US President Donald Trump has signed an executive order to temporarily suspend the approval of some green cards.
The order exempt are the spouses and young children of American citizens, green card applicants currently already in the US, and those seeking entry to work as doctors, nurses or other healthcare professionals.
But the measure is expected to curtail the practice of green card holders sponsoring their extended families, which the president calls chain migration.
The president's order is expected to face legal challenges.The order, which contains a number of exemptions, is to last for 60 days and then could be extended, he said.
Mr Trump said the policy was designed to protect American workers' jobs in an economy pummelled by the coronavirus.
Critics have accused him of using the pandemic as cover to ram through long-sought hardliner immigration policies ahead of November's election.
"This will ensure that unemployed Americans of all backgrounds will be first in line for jobs as our economy reopens," Mr Trump said at Wednesday's coronavirus briefing at the White House.
The hundreds of thousands of temporary work visas issued by the US each year will not be affected by the 60-day pause.
How did we get here?
The president vowed to suspend "all immigration" to the US on in a tweet on Monday night.
The announcement was met with a swift backlash, including from some business leaders, due to fears it could limit temporary working visas for people like farm labourers and hi-tech employees.
The final order has been heavily watered down, meaning the 60-day hold applies only to permanent residents, not temporary workers.