BEIJING — China's top Internet security official says he has "mountains of data" pointing to extensive U.S. hacking aimed at China, but 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 U.S. 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 cyberattacks launched from Chinese soil and must take action to curb high-tech spying, White House officials said on Tuesday.

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 U.S., but it's not helpful in solving the problem," said Huang Chengqing, director of the National Computer Network Emergency Response Technical Team/Coordination Center of China, known as CNCERT.

"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 United States 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 U.S. weapons systems have been compromised by Chinese hackers, the Washington Post reported late last month.

The compromised designs included combat aircraft and ships — as well as missile-defense systems vital for Europe, Asia, and the Gulf — the newspaper said, citing a report prepared for the Defense Department by the Defense Science Board.

Huang did not deny the report, but suggested that if the U.S. government wants to keep weapons programs 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.

Cyberattacks from the United States have been as serious as the accusations from Washington, Huang said

CNCERT, which issues a weekly report on cyberattacks against China, says that 4,062 U.S.-based computer servers hijacked 2.91 million mainframe computers in China.