China says it is willing to cooperate with the United States in cybersecurity after the U.S. called on it to take "serious steps" to stop cyberattacks.

Foreign Ministry spokeswoman Hua Chunying repeated China's assertion that it is firmly opposed to cyberattacks and one of the countries that has suffered most from them. She says the country cracks down on such hackers according to the law.

Hua said Tuesday: "Cyberspace needs rules and cooperation, not wars. China is willing to have constructive dialogue and cooperation with the global community, including the United States."

U.S. National Security adviser Tom Donilon's comments Monday reflect American concern over cyber intrusions and their economic costs.

Last month, a U.S.-based cybersecurity firm accused a Chinese military unit of attacking more than 140 mostly American companies.