SHANGHAI, April 6 - Visiting former U.S. Secretary of State Henry Kissinger stressed the importance of Sino-U.S. cooperation when delivering a speech on Thursday to students of the Graduate School of the Chinese Academy of Sciences in Shanghai.Kissinger said China is on the rise, but the rise of China doesn't mean the downfall of the United States. "It is not a zero-sum game. Both countries will develop through cooperation." he said.To highlight the importance of cooperation, Kissinger cited the energy issue. He said the world has developed a huge appetite for energy, but the supply of conventional energy is becoming more and more limited."The two countries need to cooperate to look for new sources of energy for the sake of everyone. There would be no winner if the two countries got into a conflict," Kissinger said.However, the two countries still face obstacles and challenges. Kissinger attributed these obstacles to different histories and cultural backgrounds."China had existed for thousands of years before the independence of the United States. China doesn't need America's permission to develop. And there is nothing we could or should do to prevent it. What we can do is to learn more about each other's history, culture and reality," Kissinger said.Kissinger arrived in Shanghai after visiting Beijing at the invitation of the Chinese Academy of Sciences (CAS), where he attended the China Forum on Science and Humanity.