Civil rights leader Jesse Jackson has pleaded with activists to remember the lessons of previous iconic protests and engage in non-violence.
As a third night of protests in New York continued, he told ITV News: "Violence has a way of distorting the message. You can't fight bullets with bricks...we will see changes."
The rally comes after the deaths of two black men, Michael Brown, who was shot dead by a white officer, and Eric Garner, who died after being put in a "choke hold" by police.
US police have also come under fire for shooting dead black 12-year-old Tamir Rice, who was playing with a toy gun.
Next weekend thousands of protesters are set to march on The Mall in Washington to demand equality and change.
ITV's US correspondent Robert Moore has this report:
A woman who filmed Eric Garner being put into a choke hold by a New York officer tells ITV News he was treated 'like a dog on the street'
Activists see a straight line from Ferguson to New York City; the police shooting of Michael Brown to the police choking of Eric Garner.