Swedish prosecutors said Thursday they have dropped three cases of sexual misconduct against WikiLeaks founder Julian Assange because they have expired, but will continue to investigate accusations of rape against him.

The Swedish Prosecution Authority said it has been unable to charge the 44-year-old Australian, who escaped a Swedish arrest warrant by taking refuge in the Ecuadorean Embassy in London in 2012 because it had not been possible to question him.

"Since the autumn of 2010, I have tried to gain permission to interview Julian Assange, but he has consistently refused to appear," said Marianne Ny, the director of public prosecution. "I still hope, however, that I will be able to arrange for an interview, as there are ongoing negotiations between Sweden and Ecuador."

The agency says that a case of sexual molestation and one of unlawful coercion expired Thursday, while a third case, of sexual molestation, would have "time-barred on Aug. 18," but added that Assange was still wanted for questioning on allegations of rape that expire in 2020.

Assange, who has denied all accusations, was wanted for questioning by Swedish police on allegations of sexual misconduct and one of rape stemming from a 2010 visit to Stockholm.

He said in London that he was "extremely disappointed" at the Swedish prosecutor's decision to continue an investigation against him.

"I am extremely disappointed. There was no need for any of this. I am an innocent man. I haven’t even been charged. From the beginning I offered a simple solution. Come to the embassy to take my statement or promise not to send me to the United States. This Swedish official refused both. She even refused a written statement. Now she has manage to avoid hearing my side of the story entirely. This is beyond incompetence. I am strong but the cost to my family is unacceptable. Even though I have been improperly treated, I would like to thank the many people in Sweden and the UK who have been very understanding of the wrong which has been done to me and my family," he said in a statement on Wikileaks.

His legal representation described the decision as: "a severe disappointment".

Additional reporting by Mashable.