Passengers arrive from Riyadh at Washington Dulles International Airport after US Supreme Court granted parts of the Trump administration's emergency request to put its travel ban into effect. Picture: James Lawler/Reuters

Washington - The US Supreme Court is allowing authorities to partially enforce President Donald Trump's ban on travellers from six Muslim-majority nations until its nine justices review the executive order later this year during the first session of its October term.

The Supreme Court said Monday it would allow the US government to enforce its ban on new visas from the six countries for individuals who have no connection to the United States.

The move marks a significant development in Trump's efforts since January to prevent travellers from Iran, Libya, Somalia, Sudan, Syria and Yemen from entering the country and to restrict refugees. The effort has been tied up in the courts for weeks amid legal challenges alleging religious discrimination and executive overreach.

The State Department said it will begin enforcing the ban in 72 hours "in an orderly fashion, consistent with the Supreme Court's unanimous order."

The department "will provide additional details on implementation after consultation with the Departments of Justice and Homeland Security," said spokeswoman Heather Nauert.

A stay on the executive order would remain in effect for those directly involved in the lower court challenges to the ban and for those experiencing similar situations to the plaintiffs, such as people with family in the United States or accepted to a US university.

The legal challengers to the ban include a man whose wife had sought a visa and a Hawaii doctor who wanted his Syrian mother-in-law to come to the United States.

Trump called the decision "a clear victory for our national security."

"As president, I cannot allow people into our country who want to do us harm," Trump said in a statement. "I want people who can love the United States and all of its citizens, and who will be hard-working and productive."

Trump's temporary halt on the US refugee programme will also be allowed to go partially into effect, but refugees with connections to relatives in the US will still be allowed, the court said.

The Supreme Court said lower courts' injunctions preventing the entire ban from taking effect had gone too far because denying entry to "foreign nationals abroad who have no connection to the United States at all ... does not burden any American party by reason of that party's relationship with the foreign national."

It noted the order itself had allowed for a case-by-case waiver system for those people with ties to the country.

The court also asked lawyers to weigh in on whether challenges to the law became moot on June 14, which would have been the 90 expiration date of the order had it taken immediate effect.

The American Civil Liberties Union welcomed the Supreme Court's decision to hear the case.

"President Trump's Muslim ban violates the fundamental constitutional principle that government cannot favor or disfavor any one religion," Omar Jadwat, director of the group's immigrants' rights project, said.

"Courts have repeatedly blocked this indefensible and discriminatory ban," Jadwat said. "The Supreme Court now has a chance to permanently strike it down."

Two US appeals courts upheld lower court decisions halting the ban to allow legal challenges on the basis of religious discrimination. The Trump administration had appealed to the Supreme Court.

The previous US appeals court decisions had found that Trump exceeded his executive authority in issuing the order and pointed to the likelihood that challenges to the measure on the grounds it discriminated against one religious group were likely to succeed.

The White House has argued that immigration law gives the president sweeping power to block entry to the United States, but challengers charge it violates the US Constitution's ban on religious discrimination and is overly broad.

Trump's first executive order aimed to block entry of citizens from seven countries and enforce a temporary stop to all refugee arrivals.

After causing widespread disruptions at international airports and protests from Muslims, rights groups and others, the order was challenged and blocked by district courts in Hawaii and Washington.

Trump then issued a revised order that blocked new visas from being issued to people from Iran, Libya, Somalia, Sudan, Syria and Yemen for 90 days and sought to halt issuances of new refugee admissions from around the world for 120 days.