Fast & Furious star Vin Diesel is rumoured to have joined the cast of Guardians of the Galaxy.

The 46-year-old star is believed to be finalising a deal, to play the tree-like alien Groot in the James Gunn-directed movie, according to Deadline.

Funnyman Jim Carrey and Adam Sandler were previously linked to the role of Groot when it was revealed they were in talks for a supporting voice role.

Guardians of the Galaxy revolves around a team of superheroes who try to save the galaxy from destruction.

The movie already has an all-star cast, including Chris Pratt, Zoe Saldana, Benicio del Toro and Glenn Close.

The movie is expected to be released in August 2014.