Movie bosses have dismissed rumours upcoming superhero movie The Green Hornet is in trouble after the film's release was delayed for a second time - they insist the extra three weeks will allow technicians to add 3D effects.

The blockbuster, starring Seth Rogen and Cameron Diaz, was originally due to hit cinemas this summer, but it was pushed back until December amid a string of production issues following the departure of director Stephen Chow.

Nicolas Cage was also rumoured to have quit the project in a dispute over his deal.

Studio heads have now announced the film will be released on 14 January to coincide with America's Martin Luther King Jr. holiday weekend - fuelling gossip about problems with the picture.

But Sony Pictures Entertainment Vice-Chair Jeff Blake is adamant the film has only been delayed so special-effects workers will have time to convert the movie into 3D.

He tells Deadline.com, "We're investing more in the film to have it 3D. We've seen part of the movie. We love it. We believe in it. Whoever is spreading these rumours has not seen it. We're going to finish Green Hornet in 3D and take nine months to do it right."