Fan said China's commitment to deal with climate change, a challenge on top of Obama's political agenda, has demonstrated to the globe its willingness to "make contributions to the international community and assume more responsibility".
"This can't be done, if China or the U.S. declines to jump in," Fan said.
Li said China's generous commitment to cope with climate change has lessened the finger-pointing from the U.S. government and their policymakers and earned more of their confidence.
Cybercrime
Neither government will engage in or knowingly support online theft of intellectual property, Xi said at a joint news conference after the summit at the White House, adding that the two sides will explore the formulation of appropriate norms of behavior in cyberspace.
The two countries have also agreed to establish a high-level dialogue mechanism on the fight against cybercrimes, Xi said.
"China and the United States are two major cybercountries and we should strengthen dialogue and cooperation," Xi said, adding that confrontation and friction are not the right choices for both sides.
Fan said the U.S. government has been trying to draw a line between commercial theft and intelligence gathering, which is not easy in practice.
"China and the U.S. have demonstrated their willingness to seek common ground, manage the disputes and come up with something that both sides could accept," Fan said.
Obama also stressed the importance for the U.S. and China to work with other countries and the UN, as well as the private sector, to start developing a protocol to govern behavior in cyberspace.
Li said as cyberspace has blurred the concept of boundaries between nations and sovereignties, it needs to have a new set of rules to deal with problems when frictions emerge among nations.
"Under the new security circumstances, big countries like China and the U.S. ought to work together and explore new rules in cyberspace."