'National Treasure' director Jon Turteltaub has given a promising update about a third movie.

The 60-year-old filmmaker directed both previous pictures in the action-adventure franchise and has now revealed that a script is being penned by a "good writer" in the hope of a third film being made.

Jon told the National Treasure Hunt podcast: "It's being written. That doesn't mean it will be finished and be great, but if it's being written it will definitely be momentous when we read it. We all know what's in it.

"But there's a very, very good writer writing it right now who tends to write really good movies. If the script comes out close to good and you can see the finish line from where you are, we're making the movie."

Turteltaub expects Nicolas Cage to return as historian Benjamin Franklin Gates along with other cast members for the third movie although he stressed that it needs to be made sooner rather than later.

Asked if the original cast will return, he said: "100 per cent. We do have to hurry because people are both getting older and less interested and lives are changing and all that.

"And the world changes. Our culture is changing. A lot. Since the first movie was made. Socially, certainly politically, and definitely, our language, and different cultural changes we've had.

"And you've got to make sure you're in touch with all that and moving with it, and doing things the right way... It's not as easy to just do another one. You've got to take a lot into account."

The director's comments contrast with those of Cage, who emphatically ruled out the possibility of a third movie earlier this year.

He told Screen Rant: "No, there is no ‘National Treasure 3’. If you want to find treasure, don't look at Disney, okay? It's not there."