Clive Owen has joined Will Smith's 'Gemini Man'.

The upcoming action thriller will see Smith play an ageing assassin who ends up getting involved in a fierce battle with his clone, who is 25 years younger than him with sharper skills.

Owen's role hasn't been revealed, though Variety report he could be the antagonist and Ang Lee is directing the Paramount movie, which has been in the pipeline since 1997.

Lee is reportedly aiming to find a second female lead soon and has met actors including Tatiana Maslany, Mary Elizabeth Winsted and Elizabeth Debicki.

The original project, set up by Disney, was pitched by Darren Lake, with Don Murphy producing and Tony Scott directing. But it was put on hold for many years to allow the visual effects technology to catch up with the film concept.

The script has been tweaked along the way, and the idea of having two different actors play the assassin and the clone was scrapped, with Smith taking on both roles as developments in filmmaking will enable him to play both different ages and fight against himself.

Jerry Bruckheimer, David Ellison, Dana Goldberg, and Don Granger are producing, with Don Murphy and Chad Oman serving as executive producers.

The film is slated for release in October 2019 and after numerous delays, it appears the movie is coming together with Owen's casting.

It is understood that Smith's schedule will need to be worked as he is also is voicing The Genie in Disney's live-action film 'Aladdin'.

Plus he will be reprising his role as Deadshot in 'Suicide Squad 2' and is to reunite with Martin Lawrence for buddy cop sequel 'Bad Boys 3'.