"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 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.

The raids have seen groups of masked, armed men in unmarked cars and armored vehicles target residential neighborhoods and businesses, sparking protests.