The release date for 'Sherlock Holmes 3' has been pushed back to 2021.

Sherlock Holmes star Robert Downey Jr.

Sherlock Holmes star Robert Downey Jr.

Last year, Warner Bros. and Village Roadshow Pictures announced that the upcoming film would hit the big screen this December - nine years after the first sequel 'Sherlock Holmes: A Game of Shadows' was released.

However, the studio has now announced that it will come out on December 21, 2021, a decade after the second film.

Robert Downey Jr. and Jude Law - who starred in the first and second films - will reprise their roles as detective Sherlock Holmes and his assistant Dr. Watson respectively.

The third instalment will be based on a script penned by Chris Brancato, while Robert's wife Susan Downey, Joel Silver and Lionel Wigram are on board to produce.

However, bosses are yet to confirm a director - meaning Guy Ritchie, who directed the first two films, may have turned down the third movie or is yet to sign a contract.

Aside from Downey Jr and Law, no other cast members have been announced.

The first 'Sherlock Holmes' film was released in December 2009, and earned $524 million globally, while the second flick 'A Game of Shadows' debuted in December 2011 and banked $545.4 million at the worldwide box office.

'Iron Man' star Robert has teased fans about his role as the private detective in the third edition of the adventure mystery film last year after he took to his social networking sites to "practice" his "Sherlock face" ahead of production.

Alongside a gif of him in character, he wrote: "Practicing my Sherlock face."