J.J. Abrams admitted it is "bittersweet" working on 'Star Wars Episode IX' without the late Carrie Fisher.

JJ Abrams

JJ Abrams

The 52-year-old director marked his first day of shooting the next installment of the hit franchise by joining Twitter, and used his first post to pay tribute to the veteran actress - who died in December 2016 - and his "extraordinary" cast and crew, as well as giving a shout out to 'Star Wars: Episode VIII - The Last Jedi' director Rian Johnson and franchise creator George Lucas.

Along with an image of a camera, J.J. - who has previously occasionally used the microblogging website through his Bad Robot company account - wrote: "Bittersweet starting this next chapter without Carrie, but thanks to an extraordinary cast and crew, we are ready to go. Grateful for @rianjohnson and special thanks to George Lucas for creating this incredible world and beginning a story of which we are lucky to be a part. #IX (sic)"

In response, Rian sent the director - who was also at the helm of the seventh movie in the franchise, 'The Force Awakens' - a gif of Harrison Ford's Han Solo saluting.

Few details are currently known about the ninth movie in the series, but it was previously revealed that unused footage from 'The Force Awakens' will be used to keep Carrie in the movie as General Leia Organa.

J.J. previously announced: "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."

Meanwhile, series veteran Mark Hamill - who portrays Luke Skywalker - also previously admitted working on the ninth movie was "bittersweet" without Carrie.

He tweeted recently: "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)"