The United States' new ambassador to China says Beijing's online theft of trade secrets represents a "major threat" to U.S. national security.
The comments on Wednesday were Max Baucus' first substantive remarks on U.S.-China relations since he became ambassador in March.
In a speech to business leaders, Baucus said the U.S. has "strong disagreements" with China over permissible behavior in cyber space.
"Cyber-enabled theft of trade secrets by state actors in China has emerged as a major threat to our economic and thus national security. Besides being criminal in nature, this behavior runs counter to China's WTO commitments. We don't sit idly by when a crime is committed in the real world. So why would we when it happens in cyber space?" said Baucus.
Baucus, a former senior lawmaker, said the U.S. will continue to use "diplomatic and legal means" to encourage China to stop the theft.
His remarks come a month after Washington charged five Chinese military officers with conducting economic espionage against U.S. companies.
China rejects the criminal allegations, the first ever leveled by the U.S. against a foreign power for cyber crimes targeting American businesses.
Beijing responded by pulling out of a regular series of discussions with the U.S. on cyber spying. It also discouraged state-owned companies from purchasing U.S.-made hardware.
Chinese cyber theft has become one of the main irritants in relations between the U.S. and China, which have the world's first and second largest economies, respectively.
The issue has been complicated by the revelations of former NSA contractor Edward Snowden, who claimed the U.S. had been hacking into computers in Hong Kong and in the mainland.
The U.S. and China have also continually bickered over other issues, such as human rights and China's increasingly aggressive behavior towards its neighbors in the disputed East and South China Seas.
On Wednesday, Baucus called for China to implement "stronger rule of law" and allow for a "more empowered civil rights society." But he said no dispute would outlast U.S.-China ties, stressing that no other relationship in the world is more important.