BERKELEY, Calif. (AP) — Berkeley, known as the home of the American free speech movement, was under heavy police watch on Thursday in advance of what was expected to be a large protest over a canceled appearance by conservative commentator Ann Coulter.

The author said she was forced to cancel a speaking event at the University of California, Berkeley, although she added that she might still "swing by to say hello" to her supporters, prompting police and university officials to brace for possible trouble.

Coulter supporters said the university was attempting to silence their views.

Dozens of police wearing flak jackets and carrying 40 mm launchers that shoot "foam batons" flanked the university's main plaza while a small group of protesters condemning Coulter staged one of two earlier rallies outside campus. Officers also took selfies with students in an attempt to lighten the mood.

Police erected barricades and refused to let participants enter the campus.

Protesters from the International Socialist Organization held what they called n "Alt Right Delete" rally with signs reading "Refuse Fascism" and "Fascist free campus." The group endorses free speech, and some members oppose the way Coulter and others have co-opted the free speech movement.

"I don't like Ann Coulter's views, but I don't think in this case the right move was to shut her down," said graduate student Yevgeniy Melguy, 24, who held a sign that read "Immigrants Are Welcome Here."

The tension illustrates how Berkeley has emerged as a flashpoint for extreme left and right forces amid the debate over free speech in a place where the 1960s U.S. free speech movement began before it spread to college campuses across the nation.

Berkeley student Joseph Pagadara, 19, said he is worried about violence and says the university is caught in the middle of the country's political divide.

"Both sides are so intolerant of each other. We are a divided country. We need to listen to each other but we're each caught in our own bubbles," he said.

As for Coulter, Pagadara said the university should have let her speak. "Now she's making herself look like the victim and Berkeley like the bad guys," he said.

KCBS reported (http://cbsloc.al/2qiK5yi ) that Gavin McInnes, founder of the pro-Trump "Proud Boys," said he will speak in the afternoon at Martin Luther King Jr. Civic Center Park and encouraged other groups to help make a large showing at the gathering.

The group on its Facebook page calls itself a fraternal organization aimed at "reinstating a spirit of Western chauvinism during an age of globalism and multiculturalism." It said it supports minimal government and is also "anti-political correctness, anti-racial guilt, pro-gun rights, anti-Drug War, closed borders." Another group called the Orange County Alt Right Group planned a rally in the same place.

In emails to The Associated Press on Wednesday, Coulter confirmed that her planned speech on illegal immigration, followed by a question-answer session, was canceled. But she remained coy about what she might do instead.

"I'm not speaking. But I'm going to be near there, so I might swing by to say hello to my supporters who have flown in from all around the country," Coulter said in an email. "I thought I might stroll around the graveyard of the First Amendment."

Officials at UC Berkeley said last week they feared renewed violence on campus if Coulter followed through with plans to speak.

They cited "very specific intelligence" of threats that could endanger Coulter and students, as Berkeley becomes a platform for extremist protesters on both sides of the political spectrum.

Efforts by the university to cancel or delay the Coulter event dealt a blow to Berkeley's image as a bastion of tolerance and free speech.

Chancellor Nicholas B. Dirks sent a letter to the campus Wednesday saying the university is committed to defending free speech but also to protecting its students.

"This is a university, not a battlefield," Dirks said in the letter. "The university has two non-negotiable commitments, one to Free Speech the other to the safety of our campus community."

Earlier this month, a bloody brawl broke out in downtown Berkeley at a pro-Trump protest that featured speeches by members of the white nationalist right. They clashed with a group of Trump critics who called themselves anti-fascists.

In February, violent protesters forced the cancellation of a speech by right-wing writer Milo Yiannopoulos, who like Coulter was invited by campus Republicans.

The Berkeley College Republicans and the Young America's Foundation, a conservative group that had helped book Coulter's campus speaking events, both pulled their support Tuesday citing fears of violence. They blamed the university for failing to ensure protection of conservative speakers.

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Associated Press writer Kristin J. Bender contributed to this report from San Francisco.