BERKELEY, Calif. (Reuters) - Conservative commentator Ann Coulter said she had scrapped plans to speak on Thursday at the University of California at Berkeley in defiance of campus officials, who had barred her original engagement this week out of concerns about inciting violent protests.

Political commentator Ann Coulter speaks during the "Politicon" convention in Pasadena, California, U.S. June 25, 2016. REUTERS/Patrick T. Fallon

Coulter, one America’s best-known and most polarizing pundits on the political right, cast blame on conservative student organizers who withdrew their invitation following their dispute with university officials.

“There will be no speech,” Coulter wrote in an email to Reuters on Wednesday. “I looked over my shoulder and my allies had joined the other team.

“I have no sponsor, no lawyer, no court order,” she said. “I can’t vindicate constitutional rights on my own.”

Coulter is the second right-wing speaker whose Berkeley appearance was scrubbed over security concerns. In February protesters started fires, broke windows and clashed with police, forcing Milo Yiannopoulos, then a senior editor for the conservative Breitbart News website, to call off his appearance.

Coulter said she might still visit Berkeley, long a bastion of liberal student activism, to meet with supporters on Thursday, the day she was originally slated to speak, but would not deliver an address on campus.

Social media feeds of militant left-wing and right-wing activists remained abuzz with vows to proceed with the demonstrations and counter-demonstrations that had been expected to accompany a Coulter appearance.

Campus officials said they were continuing to brace for unrest they see as likely on Thursday.

“Many of the individuals and organizations which planned to protest Ann Coulter’s appearance or support it still intend to come to campus,” UC Berkeley spokesman Dan Mogulof said.

He said the Berkeley College Republicans erred by inviting Coulter without notifying campus officials in advance, as is required of all student groups, and failing to submit to a “security assessment” to determine a suitable time and place for the event.

He denied that Coulter was unwelcome because of her political positions.

University officials last week rejected the original Coulter date on grounds they lacked a safe campus venue to host her speech on that day, citing the violence by left-wing protesters over Yiannopoulos’ scheduled appearance.

The university later proposed that Coulter’s speech be moved to next Tuesday. Coulter said she could not make it then and accused the school of trying to limit her audience by choosing a date that fell in a study week ahead of final exams.

After insisting she would go through with her speech on Thursday, with or without university approval, Coulter changed her mind as support from student organizers collapsed.

College Republicans spokesman Naweed Tahmas accused university officials of “refusing to ensure the safety of all students” and thus infringing on free-speech rights, as claimed in a lawsuit that sponsors of the event filed in federal court on Tuesday.

(This version of the story corrects spelling of name Naweed Tahmas in final paragraph)