The Trump administration has set new criteria for visa applicants from six mainly Muslim nations and all refugees that require a "close" family or business tie to the United States.
The move came on Wednesday after the Supreme Court partially restored President Donald Trump's executive order that was widely criticised as a ban on Muslims.
Visas that have already been approved will not be revoked, but instructions issued by the State Department say that new applicants from Syria, Sudan, Somalia, Libya, Iran and Yemen must prove a relationship with a parent, spouse, child, adult son or daughter, son-in-law, daughter-in-law or sibling already in the US to be eligible.
The same requirement, with some exceptions, holds for would-be refugees from all nations that are still awaiting approval for admission to the US.
Grandparents, grandchildren, aunts, uncles, nieces, nephews, cousins, brothers-laws and sisters-in-law, fiancees or other extended family members are not considered to be close relationships, according to the guidelines that were issued in a cable sent to all US embassies and consulates late on Wednesday.
The new rules take effect on Thursday, according to the cable, which was obtained by The Associated Press.
On Monday, the Supreme Court partially lifted lower court injunctions against Trump's executive order that had temporarily banned visas for citizens of the six countries. The justices' ruling exempted applicants from the ban if they could prove a "bona fide relationship" with a US person or entity, but the court offered only broad guidelines - suggesting they would include a relative, job offer or invitation to lecture in the US. - as to how that should be defined.
Senior officials from the departments of State, Justice and Homeland Security had laboured since the decision to clarify the ruling and Wednesday's instructions were the result.
As far as business or professional links are concerned, the State Department said a legitimate relationship must be "formal, documented and formed in the ordinary course rather than for the purpose of evading" the ban.
Journalists, students, workers or lecturers who have valid invitations or employment contracts in the US. would be exempt from the ban. The exemption does not apply to those who seek a relationship with an American business or educational institution purely for the purpose of avoiding the rules, the cable said.