Shares in Apple Computer Inc. (AAPL) fell 6 percent Friday, a day after the computer maker said it would delay the introduction of its next iMac (search) computer, which comes at the crucial back-to-school sales season.

Apple said its next iMac desktop computer won't ship until September, instead of in the coming weeks as originally planned.

"We planned our next-generation iMac ready by the time the inventory of current iMacs runs out in the next few weeks," the company said in a statement. "But our planning was obviously less than perfect."

The Cupertino, Calif.-based company has been emphasizing other computer lines for the education market -- such as its iBook notebook PC and eMac desktop computer -- which analysts said could help it avoid a shortfall.

Apple shares were down $1.92 at $30.3.

Apple's stock has outperformed other computer makers in the American Stock Exchange computer hardware index (search) by 23 percent this year -- even as it has lost market share in the personal computer market -- largely off the success of the iPod (search) music player.