Leona Lewis is refusing to release a single to promote the blockbuster 'Avatar'.

The 'Happy' singer is too busy with promotional duties for her own album 'Echo' to want to spend time plugging 'I See You', which is used in the £300 million film.

Angry director James Cameron has now given the British star a sneak preview of the movie - the most expensive ever made - in an attempt to persuade her to release the song but she is still said to be unable to make up her mind.

A source said: "Leona was delighted to be part of 'Avatar' but the song was never supposed to be released. But her cover of 'Run' wasn't meant to be released either - and look how well that did."

James is said to be particularly disappointed as he believes the track could be as successful as Celine Dion's 1997 hit 'My Heart Will Go On', the lead song on the soundtrack to his blockbuster 'Titanic'.

'I See You' was even produced by James Horner and Simon Franglen, the same team behind Celine's massive hit.