"We have to be tough, and we have to be safe, and we have to be secure. At a minimum, we have to make sure that we vet people coming into the country," the Republican president said, referring in a statement to "this era of worldwide terrorism and extremist movements bent on harming innocent civilians."

The ban prohibits entry into the United States of most people from Iran, Libya, Somalia, Syria and Yemen. The Supreme Court allowed it to go largely into effect in December while the legal challenge continued.

Senator Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, said: "Despite today's ruling, turning away those fleeing horrific violence and persecution or to discriminate against people based on nationality and religion continues to be as un-American as ever."

Writing for the court, Chief Justice John Roberts said that Trump's administration "has set forth a sufficient national security justification" to prevail.

"We express no view on the soundness of the policy," Roberts added.

The ruling affirmed broad presidential discretion over who is allowed to enter the United States. Trump could potentially add more countries to the ban.

Roberts said Trump's actions suspending entry of certain classes of people were "well within executive authority and could have been taken by any other president - the only question is evaluating the actions of this particular president in promulgating an otherwise valid proclamation."

The challengers had argued that the policy was motivated by Trump's enmity toward Muslims and urged courts to take into account his inflammatory comments during the 2016 presidential campaign. Trump as a candidate called for "a total and complete shutdown of Muslims entering the United States."