Stockholm (Agencies): The United States’ efforts to get Twitter to hand over information on the accounts of people related to WikiLeaks are outrageous, WikiLeaks founder Julian Assange has said.

"This is an outrageous attack by the Obama administration on the privacy and free speech rights of Twitter's customers—many of them American citizens," Assange said in a statement on Monday, a day before a US hearing in the case.

“It amounts to an attack on the right to freedom of association, a freedom that the people of Tunisia and Egypt, for example, spurred on by the information released by WikiLeaks, have found so valuable," the founder added.

A federal court in Alexandria, Virginia is scheduled to hold a hearing on Wednesday into the validity of a court order in December seeking Twitter to provide details about accounts belonging to Icelandic parliamentarians.

The US Department of Justice has been seeking a criminal investigation of WikiLeaks, which has obtained and published hundreds of thousands of secret US military reports and diplomatic cables.

"We are all asking all service providers to explain whether they too have been served with a similar order, and whether, they have caved into it," said the 39-year-old Assange, who is currently awaiting a London court's verdict on whether he should be extradited to Sweden to face rape and sexual molestation allegations.