Since skipping bail in 2012, the Australian-born 46-year-old has been living in the Ecuadorean embassy in London.
He fled there to avoid being extradited to Sweden to be questioned over allegations of sexual assault, which he believed were part of a plan to get him to the United States to face prosecution for leaking classified military and diplomatic documents.
Among these was a video showing U-S troops firing on Iraqi civilians and journalists.
He could face up to 45 years in jail under the US' Espionage Act.
The leaks also led to the jailing of US Private First Class Bradley Manning, now known as Chelsea Manning, whose sentence was eventually commuted by then-US President Barack Obama after serving about seven years.