San Francisco (CNN) A controversial rally in San Francisco scheduled for Saturday has been replaced with a news conference, while in nearby Berkeley the organizer of an anti-Marxism rally has requested that no one attend Sunday.

Officials from the liberal Bay Area cities had expressed concern that the rallies could attract extremists and spark violent confrontations. Organizers of both events blamed inadequate security measures for their changed plans.

The founder of Patriot Prayer, the group behind the "Freedom Rally" planned for Crissy Field Saturday, announced Friday that the event had been called off due to safety concerns.

"We have a lot of respect for the citizens in San Francisco and at the end of the day we want people to be safe," Gibson said, adding that Patriot Prayer had learned that security measures wouldn't have allowed for attendees to be searched on arrival at Crissy Field.

"So anyone could've come in and there would've been mingling antifa or whatever and also white supremacists could've showed up -- they could've come in the park and we wouldn't have been able to filter them out," he said. "In our opinion it seems like it would've been a huge riot."

Gibson said the news conference at Alamo Square Park would question the rhetoric in the city in the buildup to this weekend, including comments by House Minority Leader Nancy Pelosi, whose congressional district is in San Francisco, and San Francisco Mayor Ed Lee:

'Volatile, chaotic tinderbox'

Mayor Lee earlier said that "people with hate-filled messages" planned on coming to his city for the Crissy Field rally, while Pelosi described it as a "white supremacist rally in the middle of a park for families and children."

After Gibson announced the switch to a news conference Friday, Democratic state Sen. Scott Wiener said the Alamo Park event would be an "illegal unpermitted rally," which followed restrictions placed on Crissy Field event.

Officials had included weapons on a list of nearly 30 banned items from that rally and also planned to block cars, bikes and parking nearby.

In a statement, Wiener said the media conference at Alamo Square Park should not be allowed to take place "as a matter of public safety."

"Patriot Prayer is not interested in simply exercising free speech. Rather, Patriot Prayer wants to create a volatile, chaotic tinderbox," the senator said. "This rally in Alamo Squre is illegal and in the heart of a residential neighborhood, and I am deeply concerned it will lead to violence, particularly given how close Alamo Square is to the counter-protest at Civic Center."

Gibson suggested in a tweet that Wiener arrest him.

What's illegal is for you to move your violent rally - complete with armed militia - to a city park without getting a permit. pic.twitter.com/gvlZzuuXPR — Scott Wiener (@Scott_Wiener) August 26, 2017

'Let's not freak out'

Gibson has said in Facebook videos that he's been unfairly painted as a white supremacist by politicians when he is himself a person of color. He said the Crissy Fields event was for moderates and a way to bring together people who believe in free speech and a way "to build a healthy culture to stand against against antifa, Communists, white supremacists, Nazis."

"It's not a white supremacist rally," Gibson said in a Facebook video. "Let's not freak out. Let's not have a meltdown. Let's not have violence. Let's calm down."

Gibson is not listed as an extremist by the Southern Poverty Law Center.

Patriot Prayer organized a controversial Portland rally that came nine days after a deadly, racially charged stabbing on a commuter train. That "Trump Free Speech" rally resulted in arrests and officers deploying pepper spray. The group has also held events in places like Seattle and Olympia, Washington.

Sole attendee at rally

Across the bay in Berkeley, officials have been preparing for the "No to Marxism in America" at the Martin Luther King Jr. Civic Center Park Sunday.

The event is in protest of Marxism and the teaching of it at schools like UC Berkeley, according to organizer, Amber Gwen Cummings.

Cummings described herself as a "transsexual female who embraces diversity" and said the event was not about hate speech, with a Facebook page for the event saying racist groups were not welcome.

But according to a statement received by CNN affiliate KRON, Cummings on Friday urged people to stay away from the event over safety concerns. Cummings said she would be the sole attendee.

Although the city denied a permit for the rally, officials have been anticipating thousands to descend on Berkeley this weekend.

white supremacist and neo-Nazi groups intended to go to the event and Berkeley city officials Berkeley Mayor Jesse Arreguin earlier told reporters that there were indications on social media thatwhite supremacist and neo-Nazi groups intended to go to the event and Berkeley city officials passed a temporary rule t o give police more power to ban weapons.