The US Supreme Court ruled on Wednesday that while President Donald Trump's administration can continue to bar refugees from entering the country, officials will have to show greater flexibility in enforcing the accompanying ban on travellers from six Muslim-majority countries.

The Justice Department had asked the high court to stay an order issued last week by a federal district judge in Hawaii who found the administration's definition of close family in allowing exemptions to the travel ban was too narrow, Efe reported.

US District Judge Derrick Watson also said that the government could not prohibit entry by refugees assured of placement in the US by recognized refugee agencies.

The Supreme Court sided with the Justice Department on the refugee question, staying that portion of Watson's decision, but they supported the district judge's finding on the government's exemption criteria.

More broadly, the nine justices declined to rule definitively on the Trump administration's appeal of Watson's ruling, insisting that the case would have to follow the usual course through the federal appellate courts.

Last month, the Supreme Court set aside injunctions issued by federal appellate courts and said that portions of Trump's March 6 executive order could take effect.

That document barred citizens of Iran, Libya, Somalia, Sudan, Syria and Yemen from entering the US for 90 days and excluded all refugees for 120 days.

But in allowing the order to take effect, the Supreme Court said that the travel restrictions could not be applied to people with "a credible claim of a bona fide relationship" with a person or entity in the United States.

Under the Trump administration guidelines, spouses, parents, parents-in-law, children, sons-in-law and daughters-in-law, fiances and siblings of those already in the country can be admitted. 

But grandparents, grandchildren, aunts, uncles, nieces, nephews, cousins, brothers-in-law and sisters-in-law are excluded.

Watson struck down those restrictions.

"Common sense, for instance, dictates that close family members be defined to include grandparents," he wrote last week. 

"Indeed, grandparents are the epitome of close family members. The government's definition excludes them. That simply cannot be."