The United States did not pressure private companies to deny service to WikiLeaks following its release of secret US diplomatic cables, US Secretary of State Hillary Clinton said Tuesday.

Clinton, in a speech on Internet freedom at George Washington University here, repeated US condemnation of the release of the cables by WikiLeaks, saying it had begun with an "act of theft" and had put people at risk.

She also said the WikiLeaks case does not challenge the US commitment to Internet freedom.

Clinton said the US government had no role in the decision by a number of US companies, including Amazon, MasterCard, PayPal and Visa and Mastercard, to cut off services to WikiLeaks.

"There were reports in the days following the leak that the US government intervened to coerce private companies to deny service to Wikileaks," she said. "This is not the case.

"Some politicians and pundits publicly called for companies to dissociate from Wikileaks, while others criticized them for doing so," she said. "Public officials are part of our country's public debates, but there is a line between expressing views and coercing conduct.

"Any business decisions that private companies may have taken to enforce their own policies regarding Wikileaks was not at the direction or the suggestion of the Obama administration," Clinton said.

The US secretary of state also said the Internet was not at the heart of the WikiLeaks case.

"Fundamentally, the Wikileaks incident began with an act of theft," she said. "Government documents were stolen, just the same as if they had been smuggled out in a briefcase."

She said a government needed confidentiality to deal with sensitive issues.

"Our diplomats closely collaborate with activists, journalists, and citizens to challenge the misdeeds of oppressive governments," she said. "It's dangerous work. By publishing the diplomatic cables, Wikileaks exposed people to even greater risk."

Clinton also stressed the US commitment to an open Internet. "The fact that Wikileaks used the Internet is not the reason we criticized it," she said. "Wikileaks does not challenge our commitment to Internet freedom."

Clinton's speech came on the same day as a US judge was holding a hearing in Virginia into a US government attempt to obtain information about the Twitter accounts of people connected with WikiLeaks.

WikiLeaks founder Julian Assange described the US attempt on Monday as an "outrageous attack by the Obama administration on the privacy and free speech rights of Twitter's customers -- many of them American citizens."