J.J. Abrams has reassured fans that Carrie Fisher is "the heart" of new Star Wars movie, The Rise of Skywalker.

The late actress, who died in December 2016, appears as General Leia Organa for the last time in the Star Wars saga, thanks to unused footage from the previous movies.

And Abrams, who helmed The Force Awakens back in 2016, revealed at Disney expo D23 on Saturday that there was no way he could finish the trilogy without Fisher.

"The character of Leia is really, in a way, the heart of this story. We couldn't figure out how to tell the end of the Skywalker Saga without Leia and, you know, saying that she had passed away, saying that she was somewhere else... there was no way," the 53-year-old filmmaker told Entertainment Tonight.

"And we realised we could never recast it and we didn't want to do a CG (computer generated) character, so we actually realised there was footage we could use, that we could literally write scenes around and suddenly have as an active part of this movie and she's great in the film. And still, maybe now more than ever, it's impossible to me that she's gone because she's so alive in the film," Abrams explained.

He added that he thought Fisher would "be proud" of her integral part in the movie, that also stars Daisy Ridley, Adam Driver and Oscar Isaac.

Star Wars: The Rise of Skywalker will hit cinemas in December.

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