U.S. President Barack Obama, left, and China's President Xi Jinping, right, shake hands before their bilateral meeting at the G-20 Summit, Friday, Sept. 6, 2013 in St. Petersburg, Russia. (AP Photo/Pablo Martinez Monsivais)

Photo by: Pablo Martinez Monsivais

U.S. President Barack Obama, left, and China's President Xi Jinping, right, shake hands before their bilateral meeting at the G-20 Summit, Friday, Sept. 6, 2013 in St. Petersburg, Russia. (AP Photo/Pablo Martinez Monsivais)