The White House has set new criteria for visa applicants from six mainly Muslim countries and all refugees, requiring them to have a “close” family or business tie to the US.
The rules, affecting people from Iran, Libya, Syria, Somalia, Sudan and Yemen, are coming into force on Thursday.
They were issued after the Supreme Court partially restored President Donald Trump’s travel ban on Monday.
The executive order had been blocked by lower courts since February.
The revised rules – taking conditions laid out in the Supreme Court ruling – come into effect at 20:00 Washington time (00:00 GMT).
Who can come in?
According to the new rules, confirmed to the BBC, for the next 90 days those from the six countries without a close relationship will not be able to enter the US.
Those considered to have a close relationship under the policy include a parent, spouse, child, son or daughter-in-law, or sibling, including step- or half-siblings.
Excluded are grandparents, aunts, uncles, nieces, nephews, in-laws, extended family and grandchildren.