Nine weeks from the national U.S. election, President Donald Trump and his Democratic challenger, former Vice President Joe Biden, sparred Monday over blame for street violence linked to racial injustice and police treatment of minorities that erupted in recent days.

Trump tweeted Monday that he plans Tuesday to visit Kenosha, Wisconsin, where protests turned violent last week in the aftermath of a police shooting of a Black man as they attempted to arrest him. A white teenage vigilante claiming to protect businesses in Kenosha was accused of fatally shooting two people and wounding a third during a street demonstration.

Referring to Biden, Trump said the Wisconsin violence, and unrest in Portland, Oregon, in the U.S. northwest, forced "Slow Joe" out of his basement at his home in Delaware, where he has campaigned for the November 3 election to avoid crowds during the unabated coronavirus pandemic.

In a speech Monday in Pittsburgh, Biden blamed Trump for the violence that has erupted across the country as the United States deals with widespread and sometimes violent protests and counter-protests over police treatment of minorities and inequality in U.S. society.

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

"Does anyone believe there will be less violence in America if Donald Trump is re-elected?" Biden asked.

Oregon Governor Urges End to 'Cycle of Violence' in Portland President, Portland Mayor trade criticisms after clashes between Trump supporters and protesters

Wisconsin Governor Tony Evers urged Trump to skip his visit to the Midwestern city along the shores of Lake Michigan.

"I am concerned your presence will only hinder our healing. I am concerned your presence will only delay our work to overcome division and move forward together," Evers said.

Evers first ordered National Guard troops into Kenosha to quell the street violence after a white police officer shot Jacob Blake seven times in the back, leaving him partially paralyzed. Evers accepted more federal law enforcement assistance.

But Trump took credit on Twitter.

"If I didn't INSIST on having the National Guard activate and go into Kenosha, Wisconsin, there would be no Kenosha right now. Also, there would have been great death and injury. I want to thank Law Enforcement and the National Guard. I will see you on Tuesday!"

The White House said Trump had no plans to visit with Blake's family while he is in Kenosha.

Trump also commented again about the violence in Portland, where a caravan of Trump supporters in 600 trucks clashed Saturday with Black Lives Matter protesters demonstrating against police treatment of minorities.

During the evening, a white man was found dead in a street from a gunshot wound to the chest. Witnesses said the man was wearing a hat bearing the insignia of Patriot Prayer, a far-right group based in Washington state that has previously clashed with protesters.

Trump attacked Portland Mayor Ted Wheeler, a Democratic critic of the president, for the three months of sporadic violence in the city.

"Portland is a mess, and it has been for many years," Trump tweeted. "If this joke of a mayor doesn't clean it up, we will go in and do it for them!"

Trump also claimed, "The Radical Left Mayors & Governors of Cities where this crazy violence is taking place have lost control of their 'Movement.' It wasn't supposed to be like this, but the Anarchists & Agitators got carried away and don't listen anymore - even forced Slow Joe out of basement!"

In a statement Sunday, Biden said of Portland, "Shooting in the streets of a great American city is unacceptable. I condemn this violence unequivocally. I condemn violence of every kind by anyone, whether on the left or the right. And I challenge Donald Trump to do the same."

Biden added, "We must not become a country at war with ourselves. A country that accepts the killing of fellow Americans who do not agree with you. A country that vows vengeance toward one another. But that is the America that President Trump wants us to be. The America he believes we are."

Sunday brought continued protests in Portland, along with pledges from the state's governor to both reinforce police and address the underlying issues that have driven months of demonstrations against racial injustice.

One group of protesters went Sunday to a building used by law enforcement, and like many nights during the demonstrations, the Portland police declared the assembly "unlawful" and made arrests.

Oregon Governor Kate Brown said in a statement late Sunday that everyone, including elected officials, law enforcement and community leaders, needs to come together to stop the cycle of violence in Portland, and that "real change will come from the hard work to achieve racial justice."

Brown announced the Oregon State Police will be sending officers to Portland to free up local investigators to "arrest and charge those engaging in violent acts," and will hold a public forum with Wheeler, the Portland mayor, protest organizers and community leaders.

She also criticized the actions of "armed right-wing vigilantes" who have confronted protesters in various U.S. cities.

"The right-wing group Patriot Prayer and self-proclaimed militia members drove into downtown Portland (Saturday) night, armed and looking for a fight," Brown said. "Every Oregonian has the right to freely express their views without fear of deadly violence. I will not allow Patriot Prayer and armed white supremacists to bring more bloodshed to our streets."