Media companies have had to take on foreign governments that threatened free expression online, according to US secretary of state Hillary Clinton.
She told a Washington media gathering that the US government was "urging" media companies to challenge foreign governments' demands for censorship and surveillance.
"The private sector has a shared responsibility to help safeguard free expression. And when their business dealings threaten to undermine this freedom, they need to consider what's right, not simply what's a quick profit," she said.
Clinton was speaking following the discovery that search firm Google and at least 30 others had been attacked by China-based cyber criminals, apparently looking for details on human rights activists in China.
"New technologies do not take sides in the struggle for freedom and progress, but the United States does," she said. "We stand for a single internet where all of humanity has equal access to knowledge and ideas."
In a key speech, Clinton set out US government plans to increase free access to online information, but also to limit the harm that criminals could do online.
She said the past year had see a spike in threats to the free flow of information. China, Tunisia and Uzbekistan had stepped up censorship of the internet, while in Vietnam access to popular social networking sites had disappeared suddenly. Egypt had detained 30 bloggers and activists this month.
She said it was critical that internet users were assured of some basic freedoms. "Freedom of expression is first among them," she said.
"This freedom is no longer defined solely by whether citizens can go into the town square and criticise their government without fear of retribution. Blogs, emails, social networks and text messages have opened up new forums for exchanging ideas and created new targets for censorship," she said.
Addressing China directly, she said countries that restricted free access to information or violated the basic rights of internet users risked walling themselves off from the progress of the next century.
The US and China had different views on this, she said, adding: "We intend to address those differences candidly and consistently in the context of our positive, co-operative and comprehensive relationship."