WASHINGTON/PALM BEACH, Fla: U.S. President Donald Trump said the Justice Department will win an appeal filed late Saturday of a judge's order lifting a travel ban he had imposed on citizens of seven mainly Muslim countries.

“We'll win. For the safety of the country, we'll win," he told reporters at his private Mar-a-Lago resort in Palm Beach, Florida, shortly after the Justice Department filed a notice that it intends to appeal the order.

Trump's personal attack on U.S. District Judge James Robart in Seattle went too far for some who said the president was undermining an institution designed to check the power of the White House and Congress.

"The opinion of this so-called judge, which essentially takes law-enforcement away from our country, is ridiculous and will be overturned!" Trump said on Twitter early on Saturday.

Trump has said "extreme vetting" of refugees and immigrants is needed to prevent terrorist attacks.

Throughout the day, Trump continued to criticize the decision in tweets. Late Saturday, Trump showed no signs of backing down. "The judge opens up our country to potential terrorists and others that do not have our best interests at heart. Bad people are very happy!" he tweeted.

As the ban lifted, refugees and thousands of travelers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen who had been stopped in their tracks last weekend by Trump's executive order scrambled to get flights to quickly enter the United States.

The Justice Department did not say when it would file its appeal with the Ninth Circuit U.S. Court of Appeals of the ruling made by Robart late on Friday that also lifted Trump's temporary ban imposed on refugee admissions.

The judge appointed by former Republican President George W. Bush questioned the constitutionality of Trump's order.

The three-judge panel that will decide whether to immediately block the ruling includes appointees of George W. Bush and two former Democratic presidents, Jimmy Carter and Barack Obama.

Trump's tweets criticizing the judge's decision could make it tougher for Justice Department attorneys as they seek to defend the executive order in Washington state and other courts, said Jonathan Turley, a law professor at George Washington University, adding that presidents are usually circumspect about commenting on government litigation.

"It's hard for the president to demand that courts respect his inherent authority when he is disrespecting the inherent authority of the judiciary. That certainly tends to poison the well for litigation," Turley said.

U.S. immigration advocacy groups including the American Civil Liberties Union and International Refugee Assistance Project on Saturday in a joint statement urged those with now valid visas from the seven nations "to consider rebooking travel to the United States immediately" because the ruling could be overturned or put on hold.

A U.S. State Department email reviewed by Reuters said the department is working to begin admitting refugees including Syrians as soon as Monday.

A U.S. State Department email reviewed by Reuters said the department is working to begin admitting refugees including Syrians as soon as Monday.