WikiLeaks founder Julian Assange, who is fighting extradition to Sweden, won the right today to ask Britain's Supreme Court to hear his case, prolonging his stay in Britain.

Swedish authorities want to question the 40-year-old Australian over accusations of rape and sexual assault made by two female former WikiLeaks volunteers in August 2010.

Assange, who has been living in Britain since his arrest here in December last year, denies wrongdoing.

Two High Court judges ruled that he could ask the Supreme Court to look at his case. However, the ruling does not guarantee him a hearing. The Supreme Court, Britain's highest, can decide to hear his case, or reject his petition.

Assange now has 14 days in which to formally lodge an appeal, meaning his stay in Britain is certain to stretch into 2012.