NBC may stop offering shows on Apple’s iTunes Store after the television network confirmed that it would not be renewing its contract to sell digital downloads of its TV shows on iTunes, which account for about 40 percent of all video downloads.

Back in July Vivendi’s Universal Music Group also said it would not renew its long-term contract with iTunes. The decision by NBC further highlights the growing tensions between Apple and media companies, which are striving to get more control over the pricing strategy of their content sold on iTunes. But Apple holds firm on its stance that varying the prices of its downloads and offering discounted bundles would complicate the iTunes experience and squelch demand.

This could mark the beginning of a significant threat to Apple, which needs popular video and audio content as a way to boost sales of its money-making iPod. NBC’s current deal extends through December, so its vast video catalog will remain available on iTunes at least until then.