Cyber crimes confrontation at Obama Xi summit Mr Donilon said that Mr Xi "acknowledged" how important the issue was to Washington, and left California in no doubt where Mr Obama stood on the issue. The Washington Post recently reported that cyber attacks from China had accessed data from dozens of Pentagon weapons programs. Chinese officials said after the summit that Mr Xi opposed all forms of cyberspying and it "should not become the root cause of mutual suspicion and frictions between our two countries." Yang Jiechi, Mr Xi's senior foreign policy adviser, said the two leaders "blazed a new trail" at the casual meeting, where neckties were abandoned, and they "talked about cooperation and did not shy away from differences." It was announced that the US and China had agreed to reduce hydrofluorocarbons, a potent greenhouse gas used in refrigerators and air conditioners. Mr Donilon said the talks, which were designed to build a personal relationship between the two leaders, were "uniquely informal" and "wide-ranging." He said North Korea was discussed at length during a "lively dinner" with the leaders agreeing that neither will accept North Korea as a nuclear-armed state. He said: "China has taken a number of steps in recent months to send a clear message to North Korea, including though enhanced enforcement of sanctions and through public statements by the senior leadership in China." At the dinner of lobster tamales, porterhouse steak and cherry pie, Mr Xi spoke at length about growing up in the Chinese countryside during the cultural revolution, and broke out a bottle of the Chinese liquor Maotai to toast Mr Obama. On Saturday the US president spent half an hour having tea with Mr Xi and his wife, the singer Peng Liyuan, discussing her role as Chinese first lady. Michelle Obama had stayed in Washington where it was the end of her daughters' school year. The White House said she had written Mr Xi's wife a letter welcoming her to the United States and expressing regret for not seeing her.