The Oscar-winner played the DC comics role in 2016's Suicide Squad, though was apparently left disappointed when Warner Bros moved ahead with the new Joker movie.
According to The Hollywood Reporter, Leto complained to his agents (who also represented director Todd Phillips), and asked his music manager Irving Azoff to call the leader of Warner Bros' parent company.
The site reports that the plan was to get the studio to kill the project, though a Leto source has denied that he made the request. They also report that Azoff never made the request in the end.
Leto apparently thought that Warner Bros strung him along with the promise of a standalone movie for his Joker, and the studio thought that the Phoenix movie would be a small project.
Despite some tension over Leto's reported on-set behaviour during Suicide Squad, Leto representatives say he is still happily working with the studio.
Digital Spy has reached out to Leto's representatives for further comment.
While Leto last played the Clown Prince of Crime in the 2016 movie, earlier this year he expressed interest in returning to the role.
"I would definitely play the Joker again," he said. "It all depends on the script and the circumstances as it always does."
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