US President Donald Trump says his administration is removing the National Guard from Chicago, Los Angeles and Portland, but added federal forces will "come back" if crime rates go up.

Local leaders in those cities and Democrats have said the deployments, which have faced legal setbacks and challenges, were unnecessary.

They have accused the Trump administration of federal overreach and of exaggerating isolated episodes of violence to justify sending in troops.

Federal officers hold down a protester in the Brighton Park neighbourhood of Chicago on October 4. (AP: Chicago Sun-Times/Anthony Vazquez)

Mr Trump, a Republican, has said troop deployments in Los Angeles, Chicago, Washington, DC, Memphis and Portland were necessary to fight crime and protect federal property and personnel from protesters.

"We are removing the National Guard from Chicago, Los Angeles, and Portland, despite the fact that CRIME has been greatly reduced by having these great Patriots in those cities, and ONLY by that fact," Trump wrote on social media.

"We will come back, perhaps in a much different and stronger form, when crime begins to soar again — Only a question of time!"

Judges overseeing lawsuits filed by cities challenging the deployments have consistently ruled that the Trump administration overstepped its authority and found that there is no evidence to support claims that troops are necessary to protect federal property from protesters.

Mr Trump's announcement came shortly before a federal appellate court ruled on Wednesday that his administration had to return hundreds of California National Guard troops to Governor Gavin Newsom's control.

The California National Guard was deployed in downtown Los Angeles last June. (Reuters: David Ryder)

The US Supreme Court on December 23 blocked Mr Trump's attempt to deploy National Guard troops in Illinois, a ruling that undercut his legal rationale for sending soldiers to other states.

The court said the president's authority to take federal control of National Guard troops likely only applies in "exceptional" circumstances.

"At this preliminary stage, the Government has failed to identify a source of authority that would allow the military to execute the laws in Illinois," the court's majority held in an unsigned order.

The local leaders who opposed Mr Trump's deployment of the National Guard said on Wednesday the legal challenges compelled him to end the deployments in those cities.