US politicians and industry groups have said that Beijing is holding its currency at such a low level against the dollar that it is widening the trade gap between China and the US.

No firm deals

After his talks with Wen, Obama wrapped up his trip to China by visiting the Great Wall, before he left for South Korea.

The US president is expected to focus on the issue of North Korea's nuclear weapons programme during a meeting with Lee Myung-bak, South Korea's president, on Thursday.

Hu Jintao, China's president, and Obama promised on Tuesday to hold joint efforts on the economy, climate change and North Korea but few concrete agreements emerged from the talks.

Both sides spoke about building a "positive, co-operative, and comprehensive" relationship but steered clear of making any solid commitments, Melissa Chan, Al Jazeera's correspondent in Beijing, said.

While Obama announced that there would be a Sino-US human rights dialogue early next year, no further details were given on that.

Differences on the issues of Iran and the value of China's yuan currency were obvious from the little that was said. Obama also did not mention the issue of Tibet - an extremely sensitive subject for China.

The Chinese have been able to set the terms of Obama's trip, our correspondent said, keeping things carefully scripted in an indication that the balance of power has shifted towards China in recent years.

US 'weakened'

Even Obama's "town hall" question-and-answer session with Chinese students in Shanghai was severely restricted: broadcast only on one regional channel, no live internet coverage and a censored transcript on the web.

Jon Huntsman, the US ambassador to China, said Obama was "extremely effective" in his private meetings with Hu and other officials.

But analysts believe Obama went into the meetings with a weaker hand than most past US presidents, with US prestige battered by the economic recession as well as the wars in Iraq and Afghanistan, rubbing up against a China that is rapidly growing and gaining global clout, not to mention holding $800bn of US debt.

"The US has a lot to ask from China," Xue Chen, a researcher on strategic affairs at the Shanghai Institute for International Studies, told the Associated Press news agency.

"On the other hand, the US has little to offer China."