According to the Reuters News Agency, Assange violated the terms of his bail to enter the Ecuadorean embassy almost seven years ago. He was dragged out of the embassy last month and charged by the United States for one of the biggest ever leaks of classified information.
Judge Deborah Taylor said Assange had exploited his privileged position to flout the law and express his disdain for British justice.
Assange who is behind one of the biggest ever leaks of classified information will attend a separate hearing at Westminster Magistrates Court on Thursday (May 2) where a request by the United States for his extradition will be considered.
"Julian Assange will be sentenced at Southwark Crown Court at 10:30 tomorrow for 'violating his bail conditions' whilst seeking & obtaining political asylum," WikiLeaks said.
"On Thursday at 10AM there will be a hearing in Westminster Magistrate Court on the U.S. extradition request," it said.
The U.S. Justice Department said Assange was charged with conspiring with former Army intelligence analyst Chelsea Manning to gain access to a government computer as part of a 2010 leak by WikiLeaks of hundreds of thousands of U.S. military reports about the wars in Afghanistan and Iraq and American diplomatic communications.