A Beijing court issued the sentence Friday following a two-hour trial earlier in the week. A group of U.S and European diplomats were among those who stood outside the court after they were barred from the courtroom.
Gregory May, a political officer at the U.S. embassy in Beijing, told reporters the United States is "deeply concerned" by Liu's sentence.
"We continue to call on the government of China to release him immediately," May said, "and to respect the rights of all Chinese citizens to peacefully express their political views in favor of universally recognized fundamental freedoms, including the right to petition one's government."
May says members of the U.S. embassy have repeatedly raised Liu's case at high levels in Washington and Beijing.
China has accused foreign diplomats of "meddling" in the trial. On Thursday, Foreign Ministry spokeswoman Jiang Yu stressed that Liu is a Chinese citizen and, as a result, his case is an "internal" affair.
Liu's charge of subversion is an ill-defined one, often brought against those who voice opposition to Communist Party rule. Liu has spent time in jail or under house arrest before, especially following his early activism over the 1989 student protests in Tiananmen Square.
Liu was detained more than a year ago after he co-authored the pro-democracy petition "Charter '08." Thousands of Chinese citizens signed the online document, including 38-year-old Yang Licai. He was one of a handful of Chinese supporters who came to the courthouse on Friday. Yang says he came to turn himself in.
Yang says he also signed Charter '08, and since Liu Xiaobo was sentenced to 11 years for sponsoring the document, Yang felt he should receive the same treatment. After he finished speaking with reporters, police escorted Yang into a van that promptly drove away.
Many international human rights organizations are denouncing the sentence and calling for Liu's release. International PEN, a non-profit organization devoted to freedom of expression, called Liu's sentence "a grievous betrayal of his inalienable rights as a Chinese citizen."
Liu is a former president of the independent China PEN Center. Larry Siems, the director of Freedom to Write and international programs at PEN American Center, says Liu exemplifies the traits that PEN values.
"He's been in his work an example of a true intellectual, someone who is true to his ideas and principles," Siems noted, "and also as a public intellectual, someone who lives by his actions, his words, someone who's willing to speak his mind and take the consequences."
Siems says PEN will continue to advocate for Liu's release.