Apple has admitted its online music store will fall short of the target of 100 million sales by the end of April.
Apple is selling some 2.5 million tunes per week
In an interview with the Wall Street Journal, Apple boss Steve Jobs said he now expected to sell between 70 and 75 million tracks by then.
The iTunes store is currently selling 2.5 million songs a week.
But Apple faces increasing competition from others such as Napster, which are trying to capitalise on the appetite for online music.
Apple launched its online music store for Mac users in April 2003 and expanded it to Windows users in October.
At the time, of the Windows launch, Mr Jobs set the target of 100 million songs by April this year.
But earlier this week it became apparent that Apple might fall short of that goal, when it said that so far it had sold 50 million tracks.
"We're not going to make that number (100 million). At the rate we're at right now we'll probably have sold 70 million to 75 million songs by the end of April," Mr Jobs told the Wall Street Journal.
Part of the reason, said Mr Jobs, was due to slower than expected downloads from a Pepsi promotion.
Some 100 million songs are being given away as part of a promotion with the drinks company, but the number of sales was lower than expected.
Despite the setback, the iTunes store is doing well, selling around 2.5 million tracks every week.
The service offers tracks at 99 cents (55 pence) a song.
At the moment, the iTunes store is only available in the US. International versions of the online store are expected to be launched later this year.
Existing services such as Napster and MusicMatch are racing to catch up with Apple.
And newcomers such as Coca-Cola's site, Mycokemusic.com, have enjoyed some success in Europe, where iTunes is not yet available.