Garner, who was black, was confronted by police trying to arrest him on suspicion of selling untaxed, loose cigarettes on a Staten Island sidewalk, authorities said. Garner denied the charges and refused to be handcuffed before one of the officers placed him in what Police Commissioner William Bratton said appeared to be a chokehold, according to partial video of the encounter obtained by the New York Daily News.

On Saturday, Sharpton referred to promises by the mayor and Bratton to improve the relationship between officers and the city's minority communities.

"We are the only ones in the social setup that has to deal with fear of cops and robbers," Sharpton said.

The mayor's community affairs representative attended the rally, where he reaffirmed the city's commitment to bettering police and community relations.

"We've said from the beginning: Police work best when they have the respect from the community," Community Affairs Commissioner Marco Carrion said.

At a news conference Friday, de Blasio called the death of Garner, a father of six and grandfather of two, "a terrible tragedy."

"Chokeholds are prohibited by the New York City Police Department and by most departments," Bratton said Friday.

Along with the district attorney, police internal affairs also will investigate, Bratton and de Blasio said.

More tests are needed to determine the exact cause and manner of Garner's death, the medical examiner's office said.

In the video, Garner, who has been arrested for selling illegal cigarettes numerous times in recent years, tells two officers he hasn't done anything wrong. "Every time you see me, you want to mess with me. I'm tired of it. It stops today," Garner shouts. "I'm minding my business. Please just leave me alone."

The conversation continues until Garner says, "Don't touch me," at which point an officer behind Garner appears to put him in a chokehold. Garner sinks quickly to the ground and four officers are on him.