IN BEIJING: Chinese President Xi Jinping and United States President Barack Obama have called for a new model of cooperation between both countries, as they opened a keenly watched summit in California, but for now, cybersecurity is proving quite a thorny challenge.

Fielding questions from reporters after the first session of the two-day summit, Mr Obama voiced concerns over intellectual theft and called for "common rules of the road" with China, which has faced repeated allegations from the US of state-sponsored cyber theft on American firms.

It was a charge Mr Xi refuted indirectly, by stating that China too was a victim of cyber attacks. The Chinese leader also complained that media reports might have portrayed wrongly that China poses the main threat to cybersecurity or that "cybersecurity is the biggest problem in US-China relations".

The summit is their first meeting since Mr Xi took the presidency in March and Mr Obama began his second term in January and is unique for its informal format intended to foster personal ties and frank discussions between the leaders on issues such as global eonomic growth and North Korea's nuclear ambitions.

In opening remarks, Mr Obama said: "Our thought was that we would have the opportunity for a more extended and more informal conversation in which we were able to share both our visions for our respective countries and how we can forge a new model of cooperation between countries based on mutual interest and mutual respect."

Mr Xi said Sino-US relations have benefited from the historic 1972 meeting between former President Richard Nixon and China strongman Mao Zedong in China, but now comes a time to forge new paths to promote their domestic economies, ensure global economic stability, and address regional and global challenges.