"That has got to end," Sanders said during a major Iowa Democratic gathering Friday after listing names of African-Americans whose deaths this year involved police, the Des Moines Register reported.

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"No one will fight harder than I will to end racism in America and to reform our broken criminal justice system," Sanders added of addressing the nation's incarceration rates disproportionally affecting minorities.

He has included a variation of that line in speeches in Portland and Los Angeles over the past week that drew massive crowds after having two previous public appearances derailed by protesters affiliated with the Black Lives Matter movement.

Activists involved in the movement have pushed Sanders and others to offer more concrete solutions on race relations.

Sanders was one of many presidential candidates appearing in the early-voting state of Iowa this weekend for the State Fair and other events.