Britain's Supreme Court has endorsed the extradition of WikiLeaks chief Julian Assange to Sweden, bringing the secret-spilling Internet activist a big step closer to prosecution in a Scandinavian court.

Assange, 40, has spent the better part of two years fighting attempts to send him to the Sweden, where he is wanted for questioning in sex crime allegations. He has not been charged there.

The UK side of that struggle appeared to come to a messy end on Wednesday, with the nation's highest court ruling 5-2 that the warrant seeking his arrest was properly issued - and Assange's lawyer arguing that the case should be reopened.