Just four weeks into his administration, President Donald Trump has appeared at a campaign rally that mirrored those he staged during the election, complete with promises to repeal the health care law and fresh insults for the news media.

"I want to be among my friends and among the people," Trump told a cheering crowd packed into an airport hangar in central Florida, praising his "truly great movement".

Trump promised anew to build a border wall along the US-Mexico border, reduce regulations and create jobs. He also pledged to "do something over the next couple of days" to address the immigration order that has been blocked in the courts.

"We don't give up, we never give up," he said.

Insisting he was the victim of false reporting, Trump said his White House was running "so smoothly" and that he "inherited one big mess".

The president has been trying refocus after reports of disarray and dysfunction within his administration.

Speaking to reporters on Air Force One before the rally, Trump said he was holding a campaign rally because "life is a campaign".

"To make America great again is absolutely a campaign," he said. "It's not easy, especially when we're also fighting the press."

And he's also had to contend with crowds of protesters. Thousands of them were out on the streets of Dallas and Los Angeles to oppose immigration enforcement raids and to support immigrants and refugees generally.

Trump clearly relished being back in front of his supporters, welcoming the cheers and letting one supporter up on stage to offer praise for the president. He also enjoyed reliving his surprise victory over Democrat Hillary Clinton.

The event had the familiar trappings of a Trump campaign rally, including red Trump caps, "Make America Great Again" and "Trump/Pence" signs and at least one sign reading "Hillary for Prison".

The rally came during Trump's third straight weekend at his private south Florida club, Mar-a-Lago.

It was another working weekend for the president, who planned to interview at least four potential candidates for the job of national security adviser, a position unexpectedly open after retired General Michael Flynn's firing early this week.

Trump said on Saturday: "I have many, many that want the job, they want to really be a part of it. I'll make a decision over the next couple of days."

Trump has lurched from crisis to crisis since the inauguration, including the botched rollout of his immigration order, struggles confirming his Cabinet picks and a near-constant stream of reports about strife within his administration.