'X-Men: Days of Future Past' is ''not just a sequel''.

Director Bryan Singer - who will helm the ambitious blockbuster project, uniting the casts of the original 'X-Men' trilogy and 2011 prequel 'X-Men: First Class' - insists the new film won't just be a follow-up to the 2011 film or 2006's 'X-Men: The Last Stand', but a completely original movie.

He explained: ''We also wanted to play with the notion of different times and stuff like the way that time affects destinies. It enables the film to not just be a sequel to 'First Class' or 'X-Men 3' but to actually be its own thing.''

With a time-travelling plot, Singer was wary about the film being too confusing - but was assured it made sense by another famous director.

He said: ''I think we've got it figured out. I pitched it to James Cameron when I was in New Zealand last year and he said, 'Yes, that makes sense.' ''

Meanwhile, Singer hopes the mix of older and newer faces - including Sir Ian McKellen as Magneto from the original trilogy and Jennifer Lawrence as Mystique from 'First Class' - will entice all audiences.

He added to SFX: ''We wanted an opportunity to bring some of the favourite older and younger characters together.''

Other A-list stars who are set to reprise their roles from the various 'X-Men' films include Hugh Jackman, Sir Patrick Stewart, Halle Berry, Anna Paquin, Shawn Ashmore, Ellen Page, Michael Fassbender and James McAvoy.