Washington's efforts to get Twitter to hand over information on the accounts of people connected to WikiLeaks is "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 yesterday, a day before a US hearing in the case.

The US government's attempts to get Twitter to hand over information about the Twitter accounts of three WikiLeaks supporters, is "more shocking, at this time, (as) 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," he added.

A federal court in Alexandria, Virginia is scheduled to hold a hearing tomorrow into the validity of a court order in December requiring Twitter to provide information about accounts belonging to Icelandic parliamentarian Birgitta Jonsdottir, Jacob Appelbaum, a US computer researcher, and Rop Gonggrijp, a Dutch volunteer for WikiLeaks.

Iceland's foreign ministry last month summoned the US ambassador in Reykjavik to express "serious concern" about the bid to obtain personal information about Jonsdottir, who distanced herself from WikiLeaks a few months ago.

According to the whistleblower website, Washington is in fact demanding that Twitter, a popular microblogging site, "disclose the names, dates and locations of all persons who have used its services to receive messages from WikiLeaks or Mr. Assange."

The WikiLeaks statement yesterday described the upcoming hearing as "the scene of the first round in the US government's legal battle against Julian Assange."

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

WikiLeaks yesterday said it was glad Twitter is resisting the subpoena, but said it had appeared other service providers like Google, Facebook and Yahoo may also have received a similar demand, and "may already have provided information to the government."

"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 Assange, 39, who is himself currently awaiting a London court's decision on whether he should be extradited to Sweden to face rape and sexual molestation allegations.