President Barack Obama has said the US is "not even close" to where it needs to be in bridging the divide between police and the communities they serve.
He said more must be done to build trust among black and Hispanic people that police violence would be investigated properly.
Mr Obama was speaking in Washington after meeting activists, politicians and law enforcement officers.
It follows recent killings of black men by officers in Louisiana and Minnesota.
The killings triggered a revenge attack by a black army veteran who shot dead five police officers in the city of Dallas last week.