The city is preparing for a potentially violent showdown between dueling demonstrators Sunday, with a ramped-up police presence and vows to crackdown on clashes and criminal acts.

More than 1,000 people are expected to descend on downtown to protest a march and rally organized by Joey Gibson and his Patriot Prayer movement, which has drawn people promoting racism and white supremacy at its past events.

Right-wing demonstrators and antifascist activists have battled in the streets during numerous confrontations in Portland and around the country over the last year. Black-clad anarchists, meanwhile, have fought police and been accused of setting fires and destroying property.

Mayor Ted Wheeler issued a harsh warning to those tempted to try those tactics.

"We will not tolerate acts of violence. We will not tolerate vandalism," Wheeler said in a statement. "We will not tolerate criminal behavior. I call on everyone who plans on demonstrating here Sunday to do so peacefully, to help ensure that everyone goes home safely."

Demonstrators will begin funneling into downtown by late morning and could remain in the area until at least 5 p.m., police and organizers said. Events are scheduled to take place at Salmon Street Springs in Tom McCall Waterfront Park, Pioneer Courthouse Square and Terry Schrunk Plaza. TriMet said commuters should expect delays in downtown beginning around 11 a.m.

Portland police said in a statement that there will be a "significant law enforcement presence" during the marches and rallies — a departure from the more hands-off approach they have taken at recent demonstrations between Gibson's group and counter-protesters. Authorities will also bar firearms, knives, bats, sticks, rocks, poles and fireworks from the events.

Portland police will also receive law enforcement assistance from the Oregon State Police, Multnomah County Sheriff's Office, Federal Protective Service, the United States Attorney's Office, Multnomah County District Attorney's Office, and Portland Fire & Rescue, according to the statement.

The measures come in the wake of demonstrations that have turned violent in Charlottesville, Virginia, and Berkeley, California.

Wheeler also had some choice words for demonstrators who espouse hate.

"Portland rejects racism, bigotry, and xenophobia," he said. "We reject white supremacy. Messages of hate are not welcome in Portland."

Antifascist activists on Friday delivered a similar message by hanging large banners from area overpasses along Interstates 5, 205 and 405, as well as other roads and highways. Among the messages: "Fascism is not free speech," "Nazis thought they were patriots too," and "We are all antifa."

Gibson in recent weeks has repeatedly denounced the violence and extremists who have accompanied his rallies. Propelled into activism by Donald Trump's presidential campaign, Gibson says he has more recently tried to downplay political divisions and promote a message of unity, peace and patriotism.

-- Shane Dixon Kavanaugh

skavanaugh@oregonian.com

503-294-7632 II @shanedkavanaugh