It will be difficult to predict when supply will catch up with demand, Cook said.
Earlier this week, Apple announced that 100 million songs had been sold at its iTunes Music Store - a milestone that took three months longer than the company had hoped but still a significant benchmark that proved Apple's dominance in the online music market.
The online music store eked out a "small profit" during the quarter, Oppenheimer said.
Apple announced on July 2 a delay in the release of the next-generation iMac until September. That means Apple will miss the back-to-school rush, a critical sales period for computer makers.
The new iMac faces the same microprocessor supply problem from IBM that has already delayed Apple's Power Mac G5 product shipments, Oppenheimer said Wednesday. If the problems aren't resolved, fourth-quarter results might change, he said.
Still, Apple officials gave an optimistic outlook.
For the fourth quarter, the company expects earnings of 16 cents to 17 cents per share, including a restructuring charge of 1 cent, on revenue of $2.1 billion, Oppenheimer said. For the fiscal year, the company expects to hit $8 billion in sales, a 29 percent increase from the previous year.
