The Lincoln director revealed that he doesn't think he is a good match for a science fiction fantasy story.
Spielberg was reportedly due to receive Michael Arndt's story treatment for the next three Star Wars films, along with Brad Bird and JJ Abrams.
"No! No! It's not my genre," Spielberg told Access Hollywood when asked about Episode 7. "It's my best friend George's genre."
Spielberg and Lucas previously collaborated on the Indiana Jones series.
"I wanted to do one 15 years ago, and he didn't want me to do it," ComicBookMovie quotes Spielberg as saying. "I understand why - Star Wars is George's baby.
"It's his cottage industry and it's his fingerprints. He knows I've got Jurassic Park and Raiders. George has Star Wars and I don't think he feels inclined to share any of it with me."
Other filmmakers rumoured for the job include Matthew Vaughn (Kick-Ass, X-Men: First Class) and Colin Trevorrow (Safety Not Guaranteed).
Watch the trailer for Star Wars: The Complete Saga on Blu-ray: