Pegg, 45, is currently co-writing the third movie in the rebooted franchise and will also reprise his role as Scotty, reported Digital Spy.
Shatner did not feature in Star Trek or Star Trek Into Darkness, but has been tipped for a role in the third movie. His original series co-star Leonard Nimoy, who passed away earlier this year, appeared in both.
Pegg said the title of the film - rumoured to be Star Trek Beyond - was still "all to play for".
The writer also dismissed reports that he had been brought on the project to make it "less Star Trek-y".
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