NBC Universal, unable to come to an agreement with Apple on pricing, has decided not to renew its contract to sell digital downloads of television shows on iTunes. The media conglomerate — which is the No. 1 supplier of digital video to Apple"s online store, accounting for about 40 percent of downloads — notified Apple of its decision late yesterday, according to a person familiar with the matter who asked for anonymity because negotiations between the companies are confidential. A spokesman for NBC Universal, part of General Electric, confirmed the decision, but otherwise declined to comment. A spokesmen for Apple declined to comment. The decision by NBC Universal highlights the escalating tension between Apple and media companies, which are unhappy that Apple will not give them more control over the pricing of songs and videos that are sold on iTunes.