There'll be no Heroes, 30 Rock or The Office for U.S. users of iTunes this fall because of a dispute between Apple Inc. and NBC Universal over pricing of TV shows.

Apple, which has struck deals with other networks to sell their shows at $1.99 per episode, says it cannot reach a deal with NBC.

U.S. shows are not yet available on iTunes in Canada.

The Cupertino, Calif.-based operator of the iTunes downloading store said NBC was demanding a doubling of the wholesale price for its shows that would increase the cost for consumers to $4.99 per episode.

Apple has insisted on keeping prices low for both music and TV downloading.

NBC had earlier announced it would stop selling programs through iTunes at the end of the year because of the pricing dispute.

Apple has decided to put pressure on NBC by stopping downloading of its shows early, before the fall season starts instead of in mid-season.

NBC Universal's existing contract makes more than 1,500 hours of news, sports and entertainment available on iTunes.

It is the largest provider of paid digital video on iTunes and its products account for about 40 per cent of downloads.

Shows such as Battlestar Gallactica and Psych, among the more popular titles for downloaders, will be pulled from the iTunes store at the start of the season. Apple did not release a date for an end to its relationship with NBC.

It has struck content deals with ABC, CBS, Fox and the CW, and 50 other cable networks.