China has blasted a U.S. intelligence report accusing it of using cyber espionage to steal U.S. secrets as "irresponsible".
Chinese Foreign Ministry spokesman Hong Lei has rejected the report, and repeated Beijing's long-standing position that it wants to help.
"Online attacks are notable for spanning national borders and being anonymous," Hong said.
"Identifying the attackers without carrying out a comprehensive investigation and making inferences about the attackers is both unprofessional and irresponsible.
"I hope the international community can abandon prejudice and work hard with China to maintain online security."
The intelligence report to Congress said that so much sensitive information sits on computer networks that foreign intruders can net massive amounts of valuable data with scant risk of detection, posing a threat to U.S. prosperity and security.
Foreign intelligence services, corporations and individuals stepped up their efforts to steal information about U.S. technology that cost many millions of dollars to develop, it added, although it acknowledged the difficulty of determining who exactly is behind a cyber attack.
U.S. companies have reported intrusions into their computer networks that originated in China, but U.S. intelligence agencies cannot confirm who specifically is behind them.
Intelligence officials say it is part of the national policy of China and Russia to try to acquire sensitive technology for their own economic development, while the United States does not do economic espionage as part of its national policy.
The State Department in June said it had asked Beijing to investigate Google's allegation of a major hacking attack that the internet giant said originated in China.