The United States must develop "rules of the road" with China and other countries to mitigate cyberthreats, Pentagon chief Chuck Hagel said Thursday.
The defense secretary spoke after a Pentagon report found that Chinese hackers have gained access to secret designs for a slew of sophisticated US weapons programs, possibly jeopardizing the American military's technological edge.
Officials say the breaches described in the Defense Science Board paper were part of a broad Chinese campaign of espionage against top US defense contractors and government agencies.
"The United States knows where many of these incursions come from," Hagel told reporters on his plane as he traveled to the annual Shangri-La Dialogue, an international security conference in Singapore.
"It's pretty hard to prove that they are directed by any specific enemy but we can tell where they come from and we've got to be honest about that."
Cybersecurity is set to be discussed for the first time at a meeting of NATO defense ministers next week.
"We've got to find ways, working with the Chinese, working with everybody, (to develop) rules of the road, some international understandings," Hagel said.
The Pentagon chief said Washington would press Beijing using both public diplomacy and private talks.
"I think it's always important when dealing with other nations that you use a very significant range of options," he added.
"I've rarely seen that public engagement resolves the problem but it's important that people understand to state where they are on these issues."
During his stay in Singapore through Monday, Hagel plans to hold multiple bilateral talks with his Asian counterparts.
He pointed to an "evolving" military-to-military relationship with China.
The top US uniformed military officer, Chairman of the Joint Chiefs of Staff General Martin Dempsey visited Beijing in April and Hagel has invited his Chinese counterpart Chang Wanquan to Washington in August.
President Barack Obama is set to meet with new Chinese leader Xi Jingping next week in California.