Mr. Clinton was in Beijing as part of a four-day, seven city visit to China and gave a short speech at the U.S. Embassy for a service commemorating the Sept. 11, 2001, terror attacks.
Dressed in a dark suit and maroon tie, Mr. Clinton bowed his head in prayer and later placed his right hand over his heart as the American flag was raised to half-mast.
"I think it should be a cautionary tale for Americans, for Chinese, for people all across the world to remember what really caused this horrible act is that these people became gripped with the madness of believing that they were so right and the rest of us were so wrong that they could kill totally innocent people in pursuit of their political objectives," Mr. Clinton said.
Human rights activists had sent a letter to Mr. Clinton asking that he raise the case of a Chinese journalist sentenced to 10 years in prison under the country's vague state security laws.
The French media watchdog group Reporters Without Borders said Chinese authorities convicted Shi Tao, who had penned an e-mail about media restrictions, using information provided by Internet powerhouse Yahoo Inc.
The group said court papers showed that Yahoo Holdings (Hong Kong) Ltd., part of Yahoo's global network, helped Chinese investigators trace the personal e-mail Shi sent containing his notes on the issue.
Mr. Clinton was the keynote speaker Saturday at a conference hosted by Yahoo's new Chinese partner, Alibaba.com, at the eastern resort city of Hangzhou. He did not respond to questions from reporters about Shi's case.
He said Sunday that he was suffering from a bad cold and "didn't know about that issue until this morning."
"I would've raised it in the speech to the Internet people had I known about it," Clinton said after the ceremony at the embassy.
"The more China grows and diversifies economically and opens up to the rest of the world, the more there will have to be some room for dissent," he said. "I don't think conflicting information and debate weakens a society. I think it strengthens it."
Clinton said that the Chinese government did the right thing by releasing more information about its outbreak of severe acute respiratory syndrome after public demands flooded the Internet.
"I think that's an example of how order and debate go hand in hand because I'm not sure that it would've been handled that well if all those people hadn't rushed to the Internet and write their protests," he said.
Shi, a former journalist for the financial publication Contemporary Business News, was seized in November at his home in the northwestern province of Shanxi.
Sunnyvale, California-based Yahoo has defended its move, saying it is obliged to comply with Chinese laws and regulations.
Two of its biggest rivals, Google Inc. and Microsoft Corp.'s MSN, previously have come under attack for censoring online news sites and Web logs, or blogs, featuring content that China's communist government wants to suppress in its struggle to maintain control of information in the burgeoning Internet era.
"In the end," Clinton said, "there'll have to be more freedom of expression here."