US Democratic presidential nominee Joe Biden believes that US President Donald Trump has 'fomented' violence across the US. He has believed he is 'weak', the AFP reported, citing excerpts of his upcoming speech in Pittsburgh, released by his campaign.

"This president long ago forfeited any moral leadership in this country. He can't stop the violence because for years he has fomented it," Biden is going to say, according to the agency.

Republicans and Democrats have been exchanging harsh rhetoric while trying to pin the blame for the violent riots that have rocked the nation since the death of African American man, George Floyd, in police custody in late May. 

Earlier in the day, Trump doubled down on his decision to visit the violence-hit city of Kenosha in Wisconsin in order to meet with local law enforcement and assess the damage from the recent riots.  

"He may believe mouthing the words 'law and order' makes him strong, but his failure to call on his own supporters to stop acting as an armed militia in this country shows you how weak he is," Biden will say, according to the agency.

On Sunday, Biden accused Trump of "recklessly encouraging violence" in the country.

Mass protests against racial inequality and police brutality have continued since then. Another wave of the protests started in Wisconsin last week after a 29-year-old African American man, Jacob Blake, was shot in the back several times by a police officer in Kenosha. Blake was paralyzed from the waist down. According to the Kenosha Professional Police Association, Blake resisted arrest and refused to drop a knife he was carrying.