A prominent Chinese scholar and film critic who was scheduled to speak at an academic conference in the United States this week said Friday that she had been barred from leaving China as punishment for her commentary on human rights and free speech.

The scholar, Cui Weiping, 54, a poet and professor at the Beijing Film Academy, said that she had planned to lecture at Harvard and attend a conference sponsored by the Association for Asian Studies in Philadelphia, but that the director of her school called this week to say she had been forbidden to travel.

“I was told I had classes to teach and that the lecture I was giving was not my specialty, but those were just excuses,” said Ms. Cui, who was to have left on Wednesday. “The real reason is that they want to put pressure on me, and they want to punish me.”

Communicating through her superiors at the film academy, she said “they” — an unseen entity she described as “the authorities” — had repeatedly rebuked her for perceived sins: posting social criticism on her blog; sponsoring a seminar on the 1989 Tiananmen Square protests; and sending out Twitter messages about the jailing of Liu Xiaobo, a writer who was convicted of subversion last year for demanding increased liberties.

“These things made them unhappy,” she said, “and now they are going to make me unhappy.”...