US President Donald Trump on Monday called the nation's governors "weak" and demanded tougher crackdowns on demonstrators after another night of violent protests in dozens of cities.
Mr Trump spoke to governors in a video conference with law enforcement and national security officials, telling the leaders they “have to get much tougher" and criticising their responses.
“Most of you are weak," he said. "You have to arrest people."
The days of protests were sparked by the death of George Floyd, a black man who died after a white Minneapolis police officer knelt on his neck for several minutes.
They turned violent in several cities, with looting and mayhem, and fires ignited in the historic park across from the White House.
Mr Trump's presidential rival Joe Biden vowed to address "institutional racism" in his first 100 days in office.
Mr Biden, 77, met community leaders at a predominantly African-American church in Delaware on Monday morning.
He had left home for a second consecutive day to address racial tension that has begun to reshape November's presidential election.
Mr Biden, the former vice president who will represent Democrats against President Donald Trump, has struggled in recent weeks to be heard from his basement TV studio.
But after another night of violent protests, he met about a dozen local black leaders in his hometown before an online meeting with mayors from Los Angeles, Atlanta, Chicago and St Paul, Minnesota.
"Hate just hides," Mr Biden said, his face mask lowered around his chin, after participants shared their thoughts on police brutality.
"It doesn't go away and when you have somebody in power who breathes oxygen into the hate under the rocks, it comes out from under the rocks."
If elected, he promised to "deal with institutional racism" and set up a police regulatory body in his first 100 days in office.
Meanwhile, the lawyer for Floyd's family was set to announce findings on Monday of an independent post-mortem examination.
Floyd died after a white police officer ignored shouts from bystanders to get off his neck and Floyd's cries that he couldn't breathe.
His death, captured on video, sparked days of protests in Minneapolis that spread to cities around America.
Prosecutors say an official post-mortem examination last week said the combined effects of being restrained, possible intoxicants in Floyd's system and his underlying health issues, including heart disease, probably contributed to his death.
There were no other details about intoxicants, and toxicology results can take weeks.
In a call to police, a person said that Floyd was "awfully drunk and he's not in control of himself".
The criminal complaint said the official examination "revealed no physical findings that support a diagnosis of traumatic asphyxia or strangulation".
Ben Crump, the lawyer for Floyd's family, last week said he was commissioning a private examination.
The family's autopsy was conducted by Michael Baden and Allecia Wilson.
Mr Baden is the former chief medical examiner of New York City, who was hired to do an autopsy for Eric Garner, a black man who died in 2014 after New York police placed him in a choke-hold.
The officer who had his knee on Floyd's neck, Derek Chauvin, has been charged with third-degree murder and manslaughter, and is in custody in a state prison.
The other three officers on scene, like Mr Chauvin, were fired the day after the incident but have not been charged.
Dozens of cities across the US remain under curfews at a level not seen since riots followed the 1968 assassination of civil rights activist Martin Luther King Jr.
There was "significant ongoing" civil unrest in 36 US cities, including smaller ones such as Fargo, North Dakota, and Roanoke, Virginia, the Federal Emergency Management Agency said on Monday.
In Washington, St John's Episcopal Church, a historic place near the White House where many US presidents have gone to worship, suffered minor damage.
"The looting and destruction of property was expansive," Washington police chief Peter Newsham said.
Muriel Bowser, District of Columbia Mayor, announced on Monday that a curfew would be in place for two days starting at 7pm and lasting until the morning hours.
