Bush had shunned it as an ineffective dictators' club. Obama's team pledges to work from within to 'improve' it.
Lin Zhao, who was executed in 1968, challenged history and Mao.
In Prague speech Sunday, the US president talked about Iran, North Korea, Russia, and how to stop the spread of nuclear weapons.
Czech President Vaclav Klaus, an economist and self-proclaimed 'Euro-dissident,' is critical of much of the governing body's efforts.