President Donald Trump's administration has asked a US appeals court to rule a federal judge was wrong to suspend a travel ban the president imposed on people from seven Muslim-majority countries and all refugees.
"Congress has expressly authorised the president to suspend entry of categories of aliens," August Flentje, special counsel for the US Justice Department, said under intense questioning from a three-judge panel of the 9th US Circuit Court of Appeals.
"That's what the president did here," Flentje said at the start of an hour-long oral argument conducted by telephone and broadcast live online. He said the president's order was valid under the US Constitution.
Trump's January 27 executive order barred travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from entering for 90 days and all refugees for 120 days, except refugees from Syria, whom he would ban indefinitely.
Trump has defended the measure as necessary for national security. But individuals, states and civil rights groups challenging the ban said his administration had offered no evidence it answered a threat.
Opponents also assailed the ban as discriminatory against Muslims. It has been the most divisive act of his young presidency.
Earlier, the court said it would likely rule this week.
National security veterans, major US technology companies and law enforcement officials from more than a dozen states have backed a legal effort against the ban.
The case against the Trump administration, brought by the states of Minnesota and Washington, is ultimately likely to go to the US Supreme Court.