Swedish prosecutors have dropped their investigation into a near decade-old rape allegation against Julian Assange, removing a potential stumbling block in the U.S. government’s attempt to extradite the WikiLeaks founder on charges relating to leaking classified documents.

Sweden’s Deputy Director of Public Prosecution Eva-Marie Persson said at a press conference in Stockholm on Tuesday that after reinterviewing five witnesses, as well as two new witnesses, the evidence wasn’t strong enough to file an indictment.

The move eliminates the risk of a tussle over Mr. Assange’s extradition from the U.K., where in May he was sentenced to 50 weeks in jail for skipping bail and fleeing to the Ecuadorian embassy in 2012 in an effort to avoid extradition to Sweden to face investigation. He had been due for release in September, but a judge ordered him to remain in custody because of the risk he might abscond.

U.S. authorities have separately sought Mr. Assange’s extradition for WikiLeaks’ disclosure in 2010 of a tranche of classified documents relating to U.S. military operations supplied by former army intelligence analyst Chelsea Manning. The 48-year-old Mr. Assange is charged in the U.S. under the Espionage Act with conspiring to receive, obtaining and disclosing classified information.

Mr. Assange has long defended his actions as legitimate newsgathering that exposed alleged wrongdoing by the U.S. government.