Los Angeles, California - The first US Marines ordered by Donald Trump to Los Angeles will deploy Friday, the Pentagon said, raising the stakes in a standoff that pits the president against protesters claiming growing authoritarianism.

The approximately 200 Marines are part of a group of 700 set to join 4,000 National Guard soldiers, while local police conduct a crackdown on unrest over Trump's sweeps for undocumented migrants.

The Marines – normally used as crack troops in foreign conflicts – will be equipped with riot gear to guard a federal building starting from 12:00 PM (1900 GMT), Major General Scott Sherman told reporters.

An intense legal battle is underway over Trump's authority to deploy troops on US soil, as the country braces for widespread protests Saturday, when the Republican will be overseeing a rare large-scale military parade in Washington.

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The parade celebrates the 250th anniversary of the US Army but also coincides with Trump's 79th birthday and will be the first time tanks and other heavy weaponry have rolled through the capital city in three decades.

A "No Kings" movement has sprung up promising to stage protests in more than 2,000 places across the country in response.

Trump dispatched the California National Guard to Los Angeles last weekend following mostly peaceful, but occasionally violent protests against a surge in immigration raids in the second-largest US city.

In a show of political force, Trump overrode the objections of Democratic Governor Gavin Newsom, who usually would control the Guard. The president repeatedly exaggerated the scale of violence, claiming that without troops, Los Angeles would be "burning to the ground right now."

On Thursday, District Judge Charles Breyer ruled that Trump's actions were "illegal" and ordered that he return control of the guard to Newsom. Breyer said the LA unrest fell "far short" of the "rebellion" that Trump had described.

However, a higher court quickly paused the order pending an appeal hearing with the Trump administration next Tuesday.

The Department of Justice slammed Breyer's ruling as "an extraordinary intrusion on the President's constitutional authority as Commander in Chief."

The dispute mirrors multiple other tussles over Trump's attempts to expand the limits of presidential power, but is the first to involve troops.

The use of Marines is especially controversial, although those deploying Friday will be at a building nowhere near the site of last week's protests.