BEIJING  Liu Xiaobo, one of China’s best-known dissidents and a principal author of a pro-democracy manifesto that has attracted more than 10,000 signatures from Chinese supporters, was indicted Thursday on charges of trying to subvert the state, his lawyer said.

Mr. Liu was expected to be tried in four to six weeks, the lawyer, Shang Baojun, said Friday.

The authorities disclosed the decision to prosecute Mr. Liu  a step that almost invariably ends in imprisonment  exactly one year and a day after the manifesto, Charter 08, was published. Other Charter 08 signers said in interviews that the government was using Mr. Liu’s case to send a strong message to Chinese intellectuals that it would not tolerate organized, independent efforts to foster democracy.

“The government is trying to tell us to stop trying to push for human rights and democracy in China,” said Xu Youyu, a Charter 08 signer and a philosophy professor who recently retired from the Chinese Academy of Social Sciences. “Secondly, he has been the biggest threat inside of China, and they want to get rid of him.”

Mr. Liu’s supporters had hoped that Chinese leaders would be persuaded to release Mr. Liu, who has been detained for more than a year, when President Obama visited China last month. During the visit, United States officials gave Chinese leaders a list of “cases of concern” that included Mr. Liu and 11 other political and religious activists who are imprisoned or facing charges, according to Nicholas Bequelin, an Asia researcher for Human Rights Watch, which is based in New York.