People participate in a Yemeni protest against President Donald Trump's travel ban in the Brooklyn borough of New York City, US, February 2, 2017. [Photo/Agencies]

SAN FRANCISCO — A panel of appeals court judges reviewing President Donald Trump's travel ban hammered away Tuesday at the federal government's arguments that the states cannot challenge the order.

The hearing before the San Francisco-based 9th Circuit Court of Appeals judges was the greatest legal challenge yet to the ban, which has upended travel to the US for more than a week and tested the new administration's use of executive power.

The government asked the court to restore Trump's order, contending that the president alone has the power to decide who can enter or stay in the United States. But several states have fought the ban on travelers from seven predominantly Muslim nations and insisted that it is unconstitutional.

The judges — two Democratic appointees and one Republican — repeatedly questioned Justice Department lawyer August Flentje on why the states should not be able to sue on behalf of their residents or on behalf of their universities, which have complained about students and faculty getting stranded overseas.

Circuit Judge Michelle T. Friedland, who was appointed by President Barack Obama, asked whether the government has any evidence connecting the seven predominantly Muslim nations covered by the ban to terrorism.

Flentje told the judges that the case was moving fast and the government had not yet included evidence to support the ban.

Friedland asked if the government had connected any immigrants from the seven countries to terrorism. Flentje cited a number of Somalis in the US who, he said, had been connected to the al-Shabab terrorist group terror group after judges asked for evidence about the ban.

Flentje said the president has broad powers to protect national security and the right to assess risks based on the actions of Congress and his predecessor during the last two years.

The court was not expected to rule immediately, with a decision more likely to come later this week, court spokesman David Madden said.

Whatever the court eventually decides, either side could ask the Supreme Court to intervene.

A lawyer challenging the ban said that halting the executive order has not harmed the US government.

Instead, Washington state Solicitor General Noah Purcell told the panel, the order had harmed state residents by splitting up families, holding up students trying to travel to study and preventing people from visiting family abroad.

Judge Richard R. Clifton said he suspects it's a "small fraction" of the state's residents.