BEIJING  The harsh sentence handed down on Friday to Liu Xiaobo, one of China’s most prominent campaigners for democracy and human rights, prompted strong rebukes in the United States and Europe, but it also raised fresh questions over whether the West has much leverage over a government that is increasingly self-assured on the world stage.

By sentencing Mr. Liu to 11 years in prison for subversion, the Chinese government sent a chilling message to advocates of political reform and free speech. Mr. Liu, 53, a former literature professor who helped draft a manifesto last December that demanded open elections and the rule of law, was convicted after a closed two-hour trial on Wednesday in which his lawyers were allowed less than 20 minutes to state his case.

But many experts on Chinese politics said that Mr. Liu’s conviction on vague charges of “incitement to subvert state power” through his writing was also an unmistakable signal to the West that China would not yield to international pressure when it came to human rights. During his visit to China last month, President Obama raised Mr. Liu’s case with President Hu Jintao. Leaders of the European Union have been pressing for his release.

But a spokesman for China’s Foreign Ministry described such pressure on Tuesday as “gross interference in China’s judicial internal affairs.” The next day, more than two dozen American and European diplomats who sought to observe the trial were barred from the courthouse.