Mark Hamill thinks the late Carrie Fisher is ''simply irreplaceable''.

The 'Star Wars: The Force Awakens' actor admits it is ''bittersweet'' starring in the franchise without having Carrie - who played Princess Leia - alongside him.

He wrote on Twitter: ''It's bittersweet facing my final chapter without her. She is simply irreplaceable. I'm finding solace in the fact that she won't BE replaced & would love the worldwide outpouring of affection from those who loved her when they heard the news. #CarrieOnForever (sic)''

It was recently revealed that Carrie - who passed away in 2016 at the age of 60 - will be featured in 'Star Wars: Episode IX'.

In a statement, director J.J. Abrams said of the decision to feature Carrie: ''Finding a truly satisfying conclusion to the Skywalker saga without her eluded us. We were never going to recast, or use a CG character. With the support and blessing from her daughter, Billie, we have found a way to honour Carrie's legacy and role as Leia in Episode IX by using unseen footage we shot together in Episode VII.''

The use of Carrie's unreleased scenes comes after Disney and Lucasfilm insisted early last year they wouldn't be using CGI to recreate her likeness for the upcoming movie.

They said in a statement: ''We want to assure our fans that Lucasfilm has no plans to digitally recreate Carrie Fisher's performance as Princess or General Leia Organa. Carrie Fisher was, is, and always will be a part of the Lucasfilm family. She was our princess, our general, and more importantly, our friend. We are still hurting from her loss. We cherish her memory and legacy as Princess Leia, and will always strive to honour everything she gave to Star Wars.''