"We sent a confirmation earlier today to the prosecutors that Julian Assange agrees to be questioned in London," Olsson told AFP.
He said Assange made no specific demands about the questioning.
Swedish prosecutors offered in March to question Assange in London, dropping their previous demand that he come to Sweden to answer to the 2010 allegations, making a significant U-turn in the case that has been deadlocked for nearly five years.
Prosecutors said they had changed their stance because some of the alleged offences will reach their statute of limitations in August.
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The Australian former hacker, who has always vehemently denied the allegations and insisted the sexual encounters were consensual, has been ensconced in Ecuador's embassy in London since 2012 to avoid extradition to Sweden.
Assange has refused to travel to Sweden because he fears the country would send him to the United States, where an investigation is ongoing into WikiLeaks' release in 2010 of 500,000 classified military files on the wars in Afghanistan and Iraq and 250,000 diplomatic cables which embarrassed Washington.
Olsson said he had no information about when the questioning in London might take place.