The request was reportedly sent on Thursday, a U.S. official who spoke on condition of anonymity told The Washington Post.
The Justice Department did not immediately respond to a request for comment.
Assange was arrested on April 11 at the Ecuadoran Embassy in London on a single hacking charge from U.S. prosecutors shortly after he’d been arrested and found guilty on unrelated charges from Swedish rape accusations that are still under investigation.
In May, a federal grand jury in Northern Virginia charged Assange with 18 counts related to his work with former U.S. Army soldier Chelsea Manning, including 17 counts of espionage.
Under its treaty with Britain, the U.S. had roughly 60 days to send the request for Assange’s extradition. American officials also cannot prosecute Assange for any alleged crimes other than what they outlined in the extradition request, barring any violations that occur after he’s extradited.
Assange’s espionage charges date to 2010, when the WikiLeaks founder published a trove of classified military documents and diplomatic cables he had received from Manning. The intelligence included a video of a U.S. Apache helicopter opening fire on a group of suspected insurgents in Baghdad. Two Reuters journalists were later discovered to have been among the dead.