Robert Downey Jr. and Matt Damon will join Cillian Murphy and Emily Blunt in Christopher Nolan's upcoming drama about physicist J. Robert Oppenheimer.

Cork-born Murphy, a regular collaborator with Tenet director Nolan, will play Oppenheimer, who was known as one of the fathers of the atom bomb.

Blunt will play the physicist's wife, Katherine.

J. Robert Oppenheimer

Movie site IMDb has reported that Downey Jr. will play former United States Secretary of Commerce Lewis Strauss, and Damon will play Lt. Gen. Leslie Groves, who oversaw the development of the atomic bomb.

However, according to Deadline, who broke the casting news, neither actors’ reps have confirmed the report.

Murphy (45) has previously worked with Nolan on Dunkirk, Inception and Batman Begins.

Universal Pictures say the film will be released in North America on July 21 2023, a favoured summer slot of Nolan’s.

Universal described Oppenheimer as an "epic thriller that thrusts audiences into the pulse-pounding paradox of the enigmatic man who must risk destroying the world in order to save it".

The film is based on the 2005 Pulitzer Prize-winning book American Prometheus: The Triumph And Tragedy Of J Robert Oppenheimer by Kai Bird and the late Martin J Sherwin.

It is Nolan's first project not made at his long-time home of Warner Bros since 2000’s Memento.

The filmmaker, 51, publicly criticised Warner Bros last year when it announced its 2021 slate of films would launch on its HBO Max streaming service at the same time as in cinemas.

Nolan is one of the staunchest defenders of the theatrical experience in Hollywood.

As well as directing Oppenheimer, Nolan is writing the film’s script