A divided US appeals court ruled on Monday that Donald Trump can send National Guard troops into Portland, Oregon, despite objections by the leaders of the city and state, giving the Republican president an important legal victory as he dispatches military forces to a growing number of Democratic-led locales.

A three-judge panel of the 9th US Circuit Court of Appeals granted the Justice Department's request to put on hold a judge's order that had blocked the deployment while a legal challenge to Trump's action plays out.

The court said that sending in the National Guard was an appropriate response to protesters, who had damaged a federal building and threatened US Immigration and Customs Enforcement officers.

The unsigned majority opinion was joined by Circuit Judge Bridget Bade and Circuit Judge Ryan Nelson, who were both appointed by Trump in his first term.

Nelson also wrote a concurring opinion saying that courts have no ability to even review the president's decision to send troops.

Circuit Judge Susan Graber, an appointee of Democratic President Bill Clinton, dissented.

She said that allowing troops to be called in response to "merely inconvenient" protests was "not merely absurd" but dangerous, and she said the full 9th Circuit should overturn the ruling before Trump has a chance to send troops.

White House spokeswoman Abigail Jackson welcomed the ruling, saying Trump had exercised his lawful authority to protect federal assets and personnel from protesters.

On October 4, Portland-based US District Judge Karin Immergut, who Trump appointed during his first term as president, ruled that Trump likely acted unlawfully when he ordered troops to Portland.

She had blocked Trump from sending any National Guard troops to Portland at least until the end of October, and has scheduled a non-jury trial set to begin on October 29 to determine whether to impose a longer-term block.

In an extraordinary use of the US armed forces for domestic purposes, Trump has sent National Guard troops into Los Angeles, Washington, DC, and Memphis, and announced plans for deployments to Portland and Chicago.

Democratic-led states and cities have filed lawsuits seeking to halt the deployments, and courts have not yet reached a final decision on the legality of Trump's decisions to send the National Guard to US cities. (Reuters)