The US Customs and Border Protection (CBP) agency has issued advice to airlines allowing them to board passengers from previously barred Muslim-majority countries after a US judge temporarily halted a controversial travel ban.
The decision was taken after Seattle District Judge James Robart announced a temporary suspension of President Donald Trump's week-old executive order temporarily barring refugees and nationals from seven countries from entering the US.
Responding to the temporary block on his immigration order, Trump on Saturday dismissed the court ruling as "ridiculous".
"The opinion of this so-called judge, which essentially takes law-enforcement away from our country, is ridiculous and will be overturned!" he wrote on Twitter.
"Trump is clearly now involved in a clash with the judiciary of the US," Al Jazeera's James Bays, reporting from West Palm Beach, said.
"He is talking about a 'so-called judge' but that judge was put in place by fellow Republican President George W Bush, and when he was given the job there was a unanimous vote on Capitol Hill for him."
Earlier on Saturday, spokesmen for Qatar Airways and US-based United Airlines confirmed to Al Jazeera that they will board all passengers with valid travel documents that are affected by the order after receiving an advisory to do so from the CBP.
"As directed by the US Customs and Border Protection, nationals of the seven affected countries listed below and all refugees seeking admission presenting a valid, unexpired US visa or [green card] will be permitted to travel to the United States and will be processed accordingly upon arrival," read a travel alert posted on Qatar Airways' website.
Al Jazeera's Dorsa Jabbari, reporting from Tehran, said all airlines flying from Tehran to the US on Saturday would board Iranian nationals with valid visas.
The judge's temporary restraining order represents a major challenge to Trump's action, although his administration could still appeal against the ruling and have the policy upheld.
It comes on the heals of a week's worth of spontaneous protests at airports across the country.
The US state department said it is working with the Department of Homeland Security to work out how Friday's ruling affects its operations, and will announce any changes affecting travellers as soon as information is available.
The White House said it would file an appeal as soon as possible.
"At the earliest possible time, the Department of Justice intends to file an emergency stay of this outrageous order and defend the executive order of the president, which we believe is lawful and appropriate," the White House said in a statement. A revised statement released later omitted the word "outrageous".
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"The president's order is intended to protect the homeland and he has the constitutional authority and responsibility to protect the American people," the White House said.
Trump's executive order bars Syrian refugees indefinitely and blocks citizens of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen entry into the US for 90 days. Refugees from countries other than Syria are barred from entry for 120 days.
The state department said on Friday that up to 60,000 foreigners from the seven countries concerned had their visas cancelled as a result of the order. A justice department lawyer, however, told a court hearing in Virginia that about 100,000 visas had been revoked.
The ban caught the airline industry off guard, with some carriers forced to re-roster flight crew in order to abide by the order.
'Battle not over'
Washington Governor Jay Inslee celebrated the decision as a victory for the state, adding: "No person - not even the president - is above the law.
"There is still more to do," he said in a statement. "The fight isn't yet won. But we should feel heartened by today's victory and more resolute than ever that we are fighting on the right side of history."
The judge's decision was also welcomed by groups protesting the ban.
"This order demonstrates that federal judges throughout the country are seeing the serious constitutional problems with this order," said Nicholas Espiritu, a staff attorney at the National Immigration Law Centre.
Eric Ferrero, Amnesty International USA spokesman, lauded the short-term relief provided by the order but added: "Congress must step in and block this unlawful ban for good".
But the fluid legal situation was illustrated by the fact that the ruling came only hours after a federal judge in Boston declined to extend a temporary restraining order allowing some immigrants into the United States from countries affected by Trump's three-month ban.
A Reuters poll earlier this week indicated that the immigration ban has popular support, with 49 percent of Americans agreeing with the order and 41 percent disagreeing. Some 53 percent of Democrats said they "strongly disagree" with Trump's action while 51 percent of Republicans said they "strongly agree".
Source: Al Jazeera and news agencies