SHANGHAI (AFP) - Hong Kong actor Jackie Chan, who recently caused a stir with comments on freedom, and basketball star Yao Ming have been appointed ambassadors for next years World Expo in Shanghai, state media said. Chinas superstar pianist Lang Lang has also been given the role in a bid to help promote the event, which is expected to attract 70 million visitors, the official Xinhua news agency reported late Thursday. Chan, best-known for his martial arts films, drew strong criticism two weeks ago after he told an annual meeting of government and business leaders that China should be wary of allowing too many freedoms. I dont know whether it is better to have freedom or to have no freedom, numerous mainland news websites quoted Chan as saying at a forum in south China. With too much freedom... it can get very chaotic, could end up like in Hong Kong or like in Taiwan.... Im gradually beginning to feel that we Chinese need to be controlled. Other ambassadors for the Expo include British singer Sarah Brightman, who performed at the opening ceremony of the Beijing Olympics in August.