The Star Trek filmmaker, who is taking the directing reins on the upcoming instalment of George Lucas' sci-fi series, admitted that work is now under way for the movie, reported The Wrap.

"We're working really hard and we've got our script and we're in deep prep. Full steam ahead," he said at a Television Critics Association panel.

JJ wouldn't be drawn into the length of the film, and remained tight-lipped over the casting.

He admitted he has met with Breaking Bad star Jesse Plemons, but played down the rumours about the actors he is said to have approached for roles.

"He is one of the actors that we've talked to," the director said. "But it's not often that I read about actors that I'm going to be meeting. I get to read articles about actors who are going to come in.

"And so I get to see someone and say, 'Oh, I read that I was going to see you!'... It's usually agents talking to people about what's happening. It's a lot of noise."

JJ added: "It's sweet because it shows that there's an interest in this movie that we all obviously know is there. But it is an incredible thing to see how many crazy things get thrown out that people then often write commentaries about. How happy they are, how disappointed they are about something that is completely false."

Michael Fassbender, Hugo Weaving and Girls star Adam Driver are the latest batch of names linked to Star Wars: Episode VII, while Mark Hamill, Harrison Ford and Carrie Fisher are tipped to reprise their original roles.

The film will be released in December 18, 2015.