Several active-duty military police units have been told to be ready to deploy within four hours, if called upon to enter the US state of Minneapolis.
It comes as rioting in the city caused by the death of an unarmed African-American man at the hands of a police officer continued for a fourth consecutive night.
Protests have spread to at least 20 US cities with one person fatally shot in Detroit. Police said a 19-year-old man was killed by shots fired from a SUV, near the city's Greektown entertainment district.
The power to deploy military police can be exercised by the US president under the Insurrection Act of 1807. The last time the power was used was in 1992 during the Los Angeles riots, which were triggered by the acquittal of police officers who were filmed beating an unarmed African-American motorist.
US President Donald Trump has the power to deploy the military. Source: SIPA USA POOL
It comes as the city of Minneapolis continues to burn, with protesters setting police buildings on fire and marching through the streets, calling for all police officers involved in George Floyd’s death to be charged. Only the officer who was filmed kneeling on Mr Floyd's neck has been .
A curfew imposed by authorities in in Minneapolis failed to stop protests continuing for a fourth night. Minnesota governor Tim Walz urged residents to "go home immediately", saying officers have been shot at by protesters.
"This is not about George's death. This is not about inequities that were real. This is about chaos," he said.
Riots have spread across the United States, with larger demonstrations occurring in Los Angeles, New York, Denver, Houston, Atlanta and Louisville, Kentucky.
In Washington DC, police and secret service agents were out in force to protect the White House, with violent clashes erupting as some protesters sought to climb over barricades put in place to stop them advancing towards the government building.
In Atlanta, after hours of peaceful protests, demonstrations turned violent with cars smashed and set alight. The CNN headquarters were graffitied and crowds threw bottles at police officers, while calling for them to 'quit'.
US Secret Service form a line outside the White House as protestors attempt to breach their barricade Source: AAP
Atlanta Mayor Keisha Lance Bottoms criticised demonstrators for the violence, which she said takes away from the message of protesters. She said the violence is not "in the spirit of Martin Luther King Jr" and is "disgracing" the city.
"You are disgracing the life of George Floyd and every other person who has been killed in this country," she told protesters.
"We are better than this. We are better than this as a city.
"We are better than this as a country," she said.
