U.S. President Barack Obama delivers a speech at a dialogue with Chinese youth at the Shanghai Science and Technology Museum during his four-day state visit to China, Nov. 16, 2009.(Xinhua/Pei Xin)

U.S. President Barack Obama delivers a speech at a dialogue with Chinese youth at the Shanghai Science and Technology Museum during his four-day state visit to China, Nov. 16, 2009.(Xinhua/Pei Xin)