China's top Internet security official says he has "mountains of data" pointing to extensive US hacking aimed at China.
But Huang Chengqing, director of the National Computer Network Emergency Response Technical Team/Coordination Centre of China (CNCERT), said it would be irresponsible to blame Washington for such attacks and called for greater cooperation to fight hacking.
Cyber security is a major concern for the US government and is expected to be at the top of the agenda when President Barack Obama meets with Chinese President Xi Jinping in California on Thursday and Friday.
Obama will tell Xi that Washington considers Beijing responsible for any cyber-attacks launched from Chinese soil and must take action to curb high-tech spying, White House officials said on Tuesday.
But China's Internet security chief complained that Washington used the news media to raise cyber security concerns which would be better settled through communication, not confrontation.
"We have mountains of data, if we wanted to accuse the US, but it's not helpful in solving the problem," said Huang Chengqing.
"They advocated cases that they never let us know about," Huang said in comments on Tuesday and carried by the government-run China Daily newspaper on Wednesday.
"Some cases can be addressed if they had talked to us, why not let us know? It is not a constructive train of thought to solve problems."
CNCERT has instead co-operated with the United States, receiving 32 Internet security cases from the US in the first four months of 2013, and handling most promptly, except for a few that lacked sufficient proof, Huang said.
Designs for more than two dozen major US weapons systems have been compromised by Chinese hackers, according to a report prepared for the US Defense Department by the Defense Science Board.
Huang did not deny the report, but suggested that if the US government wants to keep weapons programmes secure, it should not allow them to be accessed online.
"Even following the general principle of secret-keeping, it should not have been linked to the Internet," Huang said.
Cyber-attacks from the United States have been as serious as the accusations from Washington, Huang said.
CNCERT, which issues a weekly report on cyber-attacks against China, says that 4,062 US-based computer servers hijacked 2.91 million mainframe computers in China.