Ann Coulter said Wednesday that she is canceling her planned speech at the University of California, Berkeley, because she had lost the backing of conservative groups that had initially sponsored her appearance.

Ms. Coulter, in a message to The New York Times, said, “It’s a sad day for free speech.”

Despite insisting that she would go to Berkeley regardless — even after the university said it could not accommodate her on the date and time it had initially scheduled her because of threats of violence — Ms. Coulter said she did not see how she could go forward. The school said she could speak only at a later date and an earlier time of day, when there were likely to be fewer students on campus and less of a likelihood for violent outbreaks.

Late on Tuesday, the conservative group that was helping Ms. Coulter in her legal efforts to force Berkeley to host her, Young America’s Foundation, said it could no longer participate. “Young America’s Foundation will not jeopardize the safety of its staff or students,” the group said.

Without any support, Ms. Coulter said, she was left with little choice. “Everyone who should believe in free speech fought against it or ran away,” she said.