The ruling is the latest step in a battle pitting the White House against liberal states who have pushed back against what they characterize as Trump's authoritarian over-reach and a creeping militarization of US society.

"After considering the record at this preliminary stage, we conclude that it is likely that the President lawfully exercised his statutory authority" when he federalized the state's National Guard, the Ninth Circuit of the US Court of Appeals said.

The ruling clears the way for 200 National Guard personnel to be deployed to protect federal buildings, where authorities say protestors -- many dressed in animal costumes -- are impeding immigration enforcement.

Portland, along with Chicago, became the latest flashpoints in the Trump administration's rollout of raids, following the deployment of troops to Los Angeles, Washington and Memphis.

In such raids, groups of masked, armed men in unmarked cars or armored vehicles target residential neighborhoods and businesses.

The state of Oregon took the administration to court to try to prevent its forces being used, obtaining a stay from a lower court that prevented any boots on the ground while the matter was decided.

Monday's decision -- by two out of the three justices on the appeals panel -- overturns the stay.

Trump has repeatedly called Portland "war-ravaged" and riddled with violent crime. But in her original ruling granting the stay, US District Judge Karin Immergut dismissed his comments as "simply untethered to the facts."

Although the city has seen scattered attacks on federal officers and property, the Trump administration failed to demonstrate "that those episodes of violence were part of an organized attempt to overthrow the government as a whole," Immergut wrote.

Protests in Portland did not pose a "danger of rebellion" and "regular law enforcement forces" could handle such incidents, Immergut said.

Circuit Judge Susan Graber, dissenting from the ruling released Monday, said the administration's seizing of Oregon's National Guard -- a force usually under the control of the state's governor -- was a dangerous erosion of constitutional rights.

"Given Portland protesters' well-known penchant for wearing chicken suits, inflatable frog costumes, or nothing at all when expressing their disagreement with the methods employed by ICE, observers may be tempted to view the majority's ruling, which accepts the government's characterization of Portland as a war zone, as merely absurd," she wrote.

"But today's decision is not merely absurd. It erodes core constitutional principles, including sovereign States' control over their States' militias and the people's First Amendment rights to assemble and to object to the government's policies and actions."

Oregon's Attorney General Dan Rayfield called for an immediate "en banc" hearing -- a gathering of the most senior judge on the circuit and 10 other justices, who could override Monday's judgment.

"Today's ruling, if allowed to stand, would give the president unilateral power to put Oregon soldiers on our streets with almost no justification. We are on a dangerous path in America," he said.

Governor Tina Kotek said she wanted to hear from Trump exactly what he expected National Guard troops to do in a city where people protest peacefully.

"The Trump Administration is being dishonest, and these actions to deploy troops are a gross, un-American abuse of power," she said.