He didn’t explicitly call on China’s leaders to lift the veil of state control that restricts Internet access and online social networking here. But President Obama did tiptoe — ever so lightly — into that controversial topic on Monday when he told students in Shanghai that a free and unfettered Internet is a source of strength, not weakness.

For Mr. Obama, who has been taking pains to strike a conciliatory note during his first visit to China, it was a rare challenge to Chinese authorities, but expressed in Mr. Obama’s now familiar nuance. Responding to a question that came via the Internet during a town hall meeting with Shanghai students — “Should we be able to use Twitter freely?” — Mr. Obama first l started to answer in the slightly off-the-point manner which he often uses when he is gathering his thoughts.

“Well, first of all, let me say that I have never used Twitter,” he said. “My thumbs are too clumsy to type in things on the phone.”

But then he appeared to gather confidence. “I should be honest, as president of the United States, there are times where I wish information didn’t flow so freely because then I wouldn’t have to listen to people criticizing me all the time,” he said. But, he added, “because in the United States, information is free, and I have a lot of critics in the United States who can say all kinds of things about me, I actually think that that makes our democracy stronger and it makes me a better leader because it forces me to hear opinions that I don’t want to hear.”

On a trip where he has gone out of his way to present a kinder and gentler image of America — bowing before Emperor Akihito in Japan (which raised the ire of right-wing bloggers back home), meeting with one of the military rulers of Myanmar, reassuring China that America doesn’t seek to contain the rising economic giant — the Twitter question, and Mr. Obama’s answer, stood out as a stark snapshot of a young American president’s efforts to reach China’s youth while not offending its authorities.

“I will no forget this morning,” one Chinese Twitterer said. “I heard, on my shaky Internet connection, a question about our own freedom which only a foreign leader can discuss.”

Interestingly, China’s government itself demonstrated some restraint, and allowed the Twitter question and Mr. Obama’s answer to stay up on websites hours after the town hall meeting.

That restraint, however, apparently only went so far. The students —some 500 —in the audience seemed handpicked by the government and many were members of the Communist Youth League, which is closely affiliated with President Hu Jintao.

That could explain some of the questions, like this one, offered by a young man who said the question came in from the Internet from a Taiwan businessman worried that some people in America were selling arms and weapons to Taiwan. “I worry that this may make our cross-straits relations suffer,” the questioner said. “So I would like to know if, Mr. President, are you supportive of improved cross-straits relations?”

Mr. Obama grabbed the out that the questioner gave him and ran with it. Making no mention of the part about arms sales to Taiwan, he instead offered up the standard American talking point on Taiwan. “My administration fully supports a one-China policy, as reflected in the three joint communiqués that date back several decades, in terms of our relations with Taiwan as well as our relations with the People’s Republic of China,” he said.

Unlike previous town hall gatherings in China with other American presidents, Mr. Obama’s question-and-answer session was not broadcast live on China’s official state network. Instead, according to the official Chinese news agency Xinhua, live broadcasts inside China were carried on the agency’s Web site and on local Shanghai stations.

The White House streamed the event live on its Web site, , which is not blocked or censored in China, and a simultaneous Chinese translation was offered. The feed also was available through the White House page on Facebook.

Unlike American town hall events, where speakers blast campaign songs while the audience chatters loudly, you could almost hear a pin drop as the students waited for Mr. Obama in an auditorium at the Museum of Science and Technology.

Qian Yu, a student from East China Normal University, said she was impressed with Mr. Obama but not happy about the limited number of questions he took. “I wish it had been a longer time,” she said after. “I had lots of questions I’d have liked to ask.”

Mr. Obama left Shanghai immediately after the town hall meeting, and flew to Beijing where he has a packed schedule: several meetings with China’s leaders, two dinners with Mr. Hu, including an elaborate state dinner Tuesday night, and tours of the Great Wall and the Forbidden City.

(www.eduwo.com, Jainlyn&Charlotte)