China must "take serious steps" to fight hacking of U.S tech networks, the Obama administration said on Monday.
National Security Adviser Tom Donilon said the sophisticated intrusions aimed mostly at business were a potential risk to U.S.-China relations.
But the senior official balanced his pointed comments with an appeal to Beijing to begin a constructive dialogue on efforts to address cybersecurity globally.
"The United States will do all it must to protect our national networks, critical infrastructure, and our valuable public and private sector property," Donilon told the Asia Society in New York.
Donilon said that American business is speaking out about its concerns with "sophisticated, targeted theft of confidential" information and "proprietary technologies through cyber intrusions emanating from China on an unprecedented scale."
Virginia-based Mandiant published a report last month alleging the Chinese government was sponsoring cyber-espionage against top U.S. companies.
China dismissed the charges, insisting that it was the victim of many cyber attacks - most originating in the United States.
But another report from Akamai Technologies, an Internet services company, said a third of all observed computer attacks from July through September last year came from China.
The United States was second, originating 13% of observed attacks, followed by Russia with 4.7%.
The Justice Department and FBI have pledged to crack down on hacking, are advising companies on how to beef up their security, and have proposed to better coordinate efforts with allies to prosecute foreign hackers.