Conservative commentator Ann Coulter said Wednesday that her planned speech at the University of California at Berkeley this week was canceled amid mounting concerns about potentially violent protests.

Coulter said in an email that the Young America’s Foundation canceled her appearance scheduled for Thursday, ordering her not to go to the Berkeley campus. Coulter wrote that the university realized the group “wasn’t serious and dropped ongoing negotiations over a room,” she wrote. “Everyone who should be for free speech has turned tail and run.”

The university sent a message to the campus community Wednesday, in the midst of uncertainty over whether, or when, Coulter might come to campus. After the university originally canceled her speech for Thursday and instead invited her to speak there next week, Coulter had vowed to speak anyway; with the university not offering a venue, campus Republican groups had been discussing her possibly appearing on a public plaza, where security would have been challenging.

Though no arrangements could be worked out, Berkeley Chancellor Nicholas Dirks emphasized that the university has two nonnegotiable commitments, to free speech and to campus safety.

“This is a University, not a battlefield,” Dirks told the university community. “We must make every effort to hold events at a time and location that maximizes the chances that First Amendment rights can be successfully exercised and that community members can be protected. While our commitment to freedom of speech and expression remains absolute, we have an obligation to heed our police department’s assessment of how best to hold safe and successful events.”

The University of California at Berkeley was girding for potentially violent protests on campus Thursday, when Coulter was expected to give a speech, potentially on Sproul Plaza, a sprawling open area on campus known for gatherings and demonstrations.

The public university has been at the center of a bitter fight over free speech, pitting protesters from the far left and the far right galvanized by Donald Trump’s election in November. Some protesters are demanding that controversial speakers not be given a platform, while others insist that blocking them violates their right to free speech. While confrontations over speakers are nothing new on college campuses, the anger has spun into riots in some places, leaving universities and police trying to balance safety and First Amendment rights.

At Berkeley, three times this year protesters wearing masks have turned demonstrations about speech into dangerous mob confrontations, with injuries, fires and massive property damage.

In February, swarms of Black Bloc protesters bent on disruption swept into the crowd of students demonstrating against Milo Yiannopoulos, then a writer for Breitbart, and within minutes broke windows and set fire to a propane tank. University officials, acting on police advice, canceled his speech because they did not feel they could ensure his or the community’s safety.

At Berkeley, the site of countless protests and the birthplace of the Free Speech Movement of the 1960s, the level of extremism was unprecedented. But canceling Yiannopoulos’ speech angered many who believe conservative opinions are being smothered at the nation’s college campuses.

In a tweet, President Donald Trump raised the threat of pulling federal funding from the university.

This spring, demonstrations in the city of Berkeley turned into violent brawls, with left-wing activists and Trump supporters, masked anarchists and self-proclaimed militia groups clashing.

Berkeley College Republicans invited Coulter to speak on campus Thursday, but university officials canceled the event because of safety concerns, suggesting she come in September instead. After a backlash, the university invited her to speak next week at a time and place they believe would be safer.

Coulter rejected that offer and vowed to come to Berkeley on Thursday despite the warnings. On Monday, student groups filed a lawsuit against university officials, contending that the school was stifling free speech, particularly for conservative students whose views are rejected by many on the liberal campus.

“It is deeply depressing and contrary to our nation’s best traditions to see violence used to silence speech with which some, or even many, may disagree,” said Will Creeley, senior vice president for legal and public advocacy at the Foundation for Individual Rights in Education. He worries that there is more of the same to come, with campuses serving as a sort of stage for these debates.

“People feel increasingly not only polarized, but also desperate. There’s a dangerous romanticization of violence – that there’s a moral imperative to take physical action to prevent speakers on campus that some find disagreeable. … There’s a sense that these speakers are not only voicing unpopular opinions but also doing some kind of physical or psychic harm to students on campus. There’s a conflation of spoken words and physical violence that I think is very dangerous and is being used, in some quarters, to justify this kind of reaction we’ve seen.”

Dirks, Berkeley’s chancellor, said Tuesday that because of the visibility around the clashes in recent months, and because of Berkeley’s iconic status – he said “everyone loves to be able to talk about how we’re the center of the ‘un-free speech movement’” – university officials are concerned that they have become an unwilling symbol.

“We feel like speakers are targeting us, precisely to provoke violent confrontations with a political purpose in mind,” Dirks said.