Edward Snowden, the former National Security Agency contractor turned whistleblower, issued a mysterious call for former colleagues to reconnect with him on Wednesday, tweeting "It's time" to his more than 2 million followers:

Snowden also quoted a tweet by journalist and author Barton Gellman, who said that he is seeking information on Snowden's work in the intelligence community so he can write Snowden's biography, and "tell it truthfully." Gellman elaborated in an encrypted message:

I'm writing a book for Penguin Press called DARK MIRROR: Edward Snowden and the American Surveillance State. I want to hear from anyone who has first-hand information on either. It need not be some deep dark secret. I'm interested in your observations about Snowden's work and work habits at CIA, Dell, NSA and Booz; or his time in the Army; or in computer training courses; or the surveillance programs and practices he described. Agree with him or not, I'd like to hear from you.

The tweet comes less than a week after Snowden exchanged Twitter barbs with WikiLeaks. The antisecrecy organization implied that Snowden was trying to win the favor of Democratic presidential nominee Hillary Clinton in order to regain entry into the US.

Snowden is living in exile in Russia after leaking information about the NSA's surveillance programs in 2013. He has previously stated that his one condition for returning to the US would be the guarantee of a fair trial and the ability to argue his case before a jury against the charges he faces under the Espionage Act.