BEIJING - A high-profile Chinese dissident accused of subversion was tried yesterday at a two-hour hearing that shut out foreign diplomats concerned over a case that reflects the communist government's deep suspicion of calls for political reform.

Liu Xiaobo was detained a year ago, just before the release of an unusually direct appeal for more civil rights in China that he cowrote called Charter 08, signed by scores of China's top intellectuals. He faces up to 15 years in jail. The verdict is due tomorrow.

International human-rights groups and Western nations have heavily criticized Liu's detention. A dozen diplomats, including from the United States, Britain, Germany, Australia and Canada, stood outside the Beijing courthouse in freezing weather, barred from entering, along with a handful of Liu's Chinese supporters.

"We call on the government of China to release him immediately," said Gregory May, first secretary with the U.S. Embassy. The European Union made a similar appeal.

Liu, 53, a literary critic and former professor, spent 20 months in jail for joining the 1989 student-led protests in Tiananmen Square that were crushed in a military crackdown. In his writings, most published only on the Internet, he has strongly called for civil rights and political reform.

Charter 08 demands a new constitution guaranteeing human rights, the open election of public officials, and freedom of religion and expression. About 10,000 people have signed it in the last year, though a news blackout and Internet censorship have left most Chinese unaware that it exists.

"As far as we can tell, this man's crime was simply signing a piece of paper that aspires to a more open and participatory form of government. That is not a crime," State Department spokesman P.J. Crowley said. "These kind of actions - clearly a political trial that will likely lead to a political conviction - are uncharacteristic of a great country."

Liu has been the only person arrested over the charter, but rights groups said several signers had been harassed or fired from their jobs, and warned not to attend the trial or write about it online.

Liu is charged with inciting to subvert state power, a vaguely worded charge that is routinely used to jail dissidents and carries a penalty of up to 15 years in prison.