“A number of state and local governments have failed to take necessary action to safeguard their residents,” Mr Trump said during an early evening Rose Garden statement with another protest over George Floyd‘s death last week while in police custody in Minneapolis. Mr Floyd was a black man; the officer who kneeled on his neck was white. “I am mobilising all available federal resources, civilian and military, to stop the rioting and looting, to end the destruction and arson, and to protect the rights of law-abiding Americans.”

Mr Trump said: “We are ending the riots and lawlessness that has spread across our country. We will end it now,” noting he had recommended during a call with governors that they activate their National guard troops, if needed. “If a city or state refuses to take the actions that are necessary to defend the life and property of their residents, then I will deploy the United States military and quickly solve the problem for them.”

President George HW Bush in 1992, during racially charged violence, “issued an executive order, which authorised the defence secretary to federalise the California National Guard and deploy active-duty army and marine personnel from bases in California to the scenes of the riots,” Mr Nevitt noted.

Mr Trump spoke as uniformed US secret service and US park police officers, backed by National Guard troops, fired tear gas at protesters about a block from the White House.

Mounted officers on horseback were used as a 1900 local time [0000 GMT] curfew set by Washington mayor Muriel Bowser approached.