But some immigration lawyers said relatively few people would fall under the ban because people coming to study, work or visit family members already have sufficient relationships with others already is in the country.

"This order, properly construed, should really allow for only the narrowest implementation of any part of the ban. It's going to be really important for us to make sure the government abides by the terms of the order and does not try to use it as a backdoor into implementing the full- scale Muslim ban," said Omar Jadwat, the American Civil Liberties Union lawyer who is representing some of the challengers to the travel ban.

The court's opinion explained the kinds of relationships people from the six countries must demonstrate to obtain a US visa.

"For individuals, a close familial relationship is required," the court said. For people who want to come to the United States to work or study, "the relationship must be formal, documented and formed in the ordinary course, not for the purpose of evading" the travel ban.

The opinion faulted the two federal appeals courts that had blocked the travel policy for going too far to limit Trump's authority over immigration. The president announced the travel ban a week after he took office in January and revised it in March after setbacks in court.

The 4th US Circuit Court of Appeals in Richmond, Virginia, said the ban was "rooted in religious animus" toward Muslims and pointed to Trump's campaign promise to impose a ban on Muslims entering the country as well as tweets and remarks he has made since becoming president.

The San Francisco-based 9th US Circuit Court of Appeals said the ban does not comply with federal immigration law, including a prohibition on nationality-based discrimination. That court also put a hold on separate aspects of the policy that would keep all refugees out of the United States for 120 days and cut by more than half, from 110,000 to 50,000, the cap on refugees in the current government spending year that ends Sept. 30.

Trump's first executive order on travel applied to travelers from Iraq and well as the six countries, and took effect immediately, causing chaos and panic at airports as the Homeland Security Department scrambled to figure out whom the order covered and how it was to be implemented.

A federal judge blocked it eight days later, and that was upheld by a 9th circuit panel. Rather than pursue an appeal, the administration said it would revise the policy.

In March, Trump issued the narrower order.

AP