Kucherena is completing a trilogy which tells the story of a US whistle-blower and is loosely based on Snowden's experiences. The first part, dubbed the "Time of the Octopus", will be published shortly.

"He (Stone) met with me, he did not meet with Snowden. The book will be published later," Kucherena said, adding he had met the director three times at his home.

He said his world-famous client knows about Stone's plan to make a movie about him and his reaction was "absolutely normal."

The lawyer said he had written the novel because he could not remain indifferent to his client's ethical dilemma.

"I have become a witness to the moral paradox, so to speak," Kucherena told AFP. "I have become imbued with his emotional state, he transported me into his world," he said of the American.