PORTLAND, Ore. — The city's police response will be tested Saturday morning when potentially hundreds of people with clashing ideologies converge on a downtown waterfront park, a showdown that Portland leaders fear could devolve into violent street brawls.

Portland police will be joined by other local, state and federal agencies, and participants who are asked to stay on sidewalks and fail to comply could face arrest, warned Lt. Tina Jones, a spokeswoman for the Portland Police Bureau. She confirmed that the city had received no permit applications for a mass gathering of people.

"A lot of this is seeing who shows up on game day," Jones said at a news conference Friday.

Police have been scouring social media for insight and developments into Saturday's event, which is being organized by members of the Proud Boys, whose founder has described it as a "fraternal organization" for young "Western chauvinist" men. The goal of the "End Domestic Terrorism" rally, they say, is to get self-described anti-fascists, known collectively as antifa, declared as a domestic terrorist organization.

Organizer Joe Biggs told The Associated Press that those coming to Portland have been asked not to bring weapons or start fights, but they will defend themselves if attacked.

Other affiliated far-right and white nationalist groups from across the country could also show up in Portland, officials have said. But participation could be more muted after heightened attention to large gatherings in the wake of the mass shootings in El Paso, Texas, and Dayton, Ohio.

Extremism researcher JJ McNabb tweeted this week that Biggs began disappearing from various social media platforms and that the Oathkeepers, an extremist anti-government militia, said it wouldn't attend.

Oregon's largest city — in recent years a hub of progressivism made hip in the TV show "Portlandia" — has turned into a divisive battleground with the election of President Donald Trump.

Trump last month tweeted that antifa was made up of "Radical Left Wack Jobs" and a "major Organization of Terror."

Two members of Rose City Antifa, the nation's oldest active anti-fascist group, told NBC News that supporters will show up Saturday and "defend our community from people who want to do it harm."

They said it's their duty to stand up against the far-right because "we've seen them just attack people on the street, who were essentially bystanders."

The streets of Portland have become a powder keg over the past year during various protests involving far-right groups and antifa, with reports of projectiles being fired, arrests and injuries. In those instances, police have declared the situation a riot and used flash bangs and rubber bullets to disperse crowds.

Patriot Prayer, a gun rights and pro-Second Amendment group, had organized many of the rallies, drawing interest from white supremacists and white nationalists.

Its leader, Joey Gibson, might not attend as he was wanted on criminal rioting charges related to an event on May 1, when fights erupted among Patriot Prayer members at a Portland bar. He turned himself in to authorities on Friday and was released Friday evening.

Gibson was also in the spotlight earlier this year when a local news outlet, the Willamette Week, reported he shared friendly text messages with the police commander of the department's rapid response team.

Mayor Ted Wheeler ordered an independent investigation into the potential existence of bias in the actions of the police leading up to and during demonstrations involving the far-right and anti-fascists.

Jones said Friday that the police's primary mission will be to "keep people safe while making sure people express their First Amendment rights."

"Our interactions should not be construed as bias, preference or endorsements of any particular point of view or side," she added.

Chaos also broke out during a rally in June, when masked antifa members physically attacked conservative blogger Andy Ngo in an incident shared on social media.

Portland police tweeted that protesters may have thrown milkshakes with quick-dry cement, although they had no physical evidence those were deployed.

After a confrontation between authorities and protesters, police use pepper spray as multiple groups, including Rose City Antifa and the Proud Boys, protest in downtown Portland, Oregon, in June 2019. Dave Killen / AP

Vegan milkshakes, however, were handed out during the rally by people trying to thwart the far-right's message.

Supporters of the movement (Pop)ular (Mob)ilization, or Pop Mob, will attempt to do the same on Saturday when they host an event called "The Spectacle," featuring a mask-decorating station, a banana costume dance party and people dressed up as the poop emoji. Organizers say it's a way to downplay the far-right's rhetoric and inject the atmosphere with whimsy and "joyful resistance."

"We know one of the far-right's largest recruiting tactics is making slickly edited videos of themselves and their toxic masculinity in riot form. They share it on the internet and it's effective in getting more people to get into their violent activities," said Effie Baum, a Pop Mob spokesperson.

Baum said that while people's safety can't be guaranteed, its supporters aren't necessarily looking to confront the far-right.

"Having a conversation is useless. We're not going to change their minds," Baum said. "But we can make sure their videos are filled with poop emojis and a lot of music."

Gregory McKelvey, a Portland organizer who has been critical of the police response toward counter-protesters, said it's important to show that the flash points of violence can be small, and that the people of the city don't support messages of intolerance and hate.

"It looks like anarchy," he said. "That's not what Portland is about."

Dasha Burns and Abigail Brooks reported from Portland, and Erik Ortiz from New York.