The three-day conference was to begin Thursday in Beijing, but speakers were told to "assume that it's been canceled," pending official notice, said Bruce Gilley, the author of several books on Chinese politics who was invited to speak at the conference.
It would be the second time in six months that China has called off an international conference on a sensitive issue, after scrapping a meeting in December on labor standards with foreign union officials.
The communist government has reached out to foreign scholars on a wide range of topics including political reform in recent years, but Chinese leaders keep a tight rein on political events. Sensitivities are highest around June 4 and other major anniversaries.
Topics for the conference this week included elections, labor rights and government reform. It was organized by the China University of Political Science and Law and New York City's Fordham University.
"This was a conference that really highlights the growing amount of interest in Chinese universities about serious democratization," Gilley said in a telephone interview from the United States.
However, he said, "Like typical dictators, (the government's) only reaction is to crush and repress it instead of accommodating it."
A woman who answered the phone at the law school of the China University of Political Science and Law said she had heard the conference was canceled but didn't know why. She would not give her name.
At least 30 scholars from the United States and China were to speak at the conference, which aimed to "assess the present state and future of human rights, democracy and constitutionalism in China."
China holds nonpartisan elections for low-level village offices -- a practice the government describes as democratization -- but policies are decided by the Communist Party. Most independent political activity is banned, and activists who want an end to the party's monopoly on power are regularly imprisoned and harassed.
Every year as June 4 nears, authorities step up surveillance of political activists and people killed in the 1989 crackdown.
Chinese troops killed hundreds and possibly thousands of people when they crushed demonstrations centered on Tiananmen Square in Beijing.
Chinese leaders often say the rights to food, housing and other benefits of economic development are paramount. They reject criticism of their suppression of religious rights and pro-democracy activists.