The US has called on Beijing to investigate the recent cyber attacks on Google, which have prompted the search giant to threaten to leave China.
Secretary of State Hillary Clinton said that companies such as Google should refuse to support "politically-motivated censorship".
She also said China along with Tunisia and Uzbekistan had boosted censorship.
Google says hackers tried to infiltrate its software coding and the e-mail accounts of human rights activists.
The BBC's Kim Ghattas at the State Department says Mrs Clinton's remarks are bound to anger the Chinese authorities, who have sought to play down the incident.
China says the row should not be linked to relations with the US.
Vice-Foreign Minister He Yafei said the rift with the web company should not be "over-interpreted", according to state news agency Xinhua.
Transparency call
In a wide-ranging speech at the Newseum journalism museum in Washington, Mrs Clinton said the internet had been a "source of tremendous progress" in China, but that Beijing should investigate the attacks on Google.
"We look to Chinese authorities to conduct a thorough investigation of the cyber intrusions," she said.
"We also look for that investigation and its results to be transparent."
Again in reference to China, she said that any country which restricted free access to information risked "walling themselves off from the progress of the next century".
The US intended to address issues of internet freedom within its relationship with Beijing, she added.
Separately, she called for tough action against people and states that carried out cyber attacks.
 Google says it will stay in China if censorship is relaxed |
"Countries or individuals that engage in cyber attacks should face consequences and international condemnation," she said.
"In an interconnected world, an attack on one nation's networks can be an attack on all."
Mrs Clinton addressed a number of other issues in the speech:
- She named Tunisia, Uzbekistan, Vietnam and Egypt, as well as China, as countries where the "free flow of information" was threatened
- She said the US was supporting the development of new tools to enable citizens to circumvent politically motivated censorship
- Internet technologies were a mixed blessing, used by terror groups to spread hatred and by authoritarian governments to crush dissent
- She cited Saudi Arabia as an example of countries which blocked access to information about religions, including Islam
- Countries that employed censorship could make no distinction between political and commercial speech and were therefore harming their own interests
Mobile launch postponed
Google said on 12 January hackers had tried to infiltrate its software coding and the e-mail accounts of Chinese human rights activists, in a "highly sophisticated" attack.
The California-based company, which launched in China in 2006, said it would quit the country unless the government relaxed censorship.
On Tuesday, the Chinese government said Google and other foreign companies had to obey the country's laws and traditions.
The same day, Google said it was postponing the launch of two mobile phones in China.
When Google launched google.cn four years ago, it was criticised for agreeing to Beijing's demands to make certain search results off-limits - including those relating to the 1989 Tiananmen Square protests, Tibetan independence or Falun Gong.
China has more internet users, about 350 million, than any other country and provides a lucrative search-engine market worth an estimated $1bn (£618m) last year.
Google holds about a third of the country's search market, with Chinese rival Baidu having more than 60%.