Guillermo Del Toro is writing a sequel to 'Pacific Rim'.

The filmmaker has confirmed he has begun work on a follow-up to his blockbuster monsters-versus-robots movie, but insists it's up to Warner Bros. and Legendary Pictures to decide if the script will go into production.

He told IGN: ''We are writing the sequel. Travis Beacham and I are writing, so that is active. The decision to greenlight or not, that's definitely above my pay rate.''

'Pacific Rim' was released in July and while it experienced a soft opening in the United States, it has performed strongly worldwide and is currently the highest grossing blockbuster movie of the year that is based on an original concept.

Most of the film's $400 million worldwide gross is based on international takings; the movie has particularly performed well in China.

The film starred Charlie Hunnam, Idris Elba, Rinko Kikuchi, Charlie Day and many more.

Lead actor Hunnam recently dropped out of his role as Christian Grey in an adaptation of best-selling erotic novel 'Fifty Shades of Grey', which would leave him open to return for a sequel.

The actor previously revealed del Toro was so pleased with his performance in 'Pacific Rim', he has vowed to cast him in all of his English language movies.