Apple’s fourth-quarter profits will fall short of those posted a year ago, because of its failure to meet demand for its recently announced Power Mac G4 computers.

Apple cited a shortage of the high-performance G4 processors - supplied by Motorola - for the G4 demand bottleneck.

"We are very disappointed that this quarter's deliveries of G4 processors will be lower than planned. Orders for the Power Mac G4 have been strong and we anticipate ending the September quarter with a substantial order backlog," Fred Anderson, Apple's chief financial officer, said in a statement issued today.

Apple expects to report earnings of $75 million to $85 million for the quarter, which is due to end on 30 September. This compares with earnings of $106 million a year ago, the company said. The fourth-quarter results are due on 13 October. For the December quarter, Apple still expects computer shipments and revenues to increase significantly from a year ago.

Motorola put a positive spin on the news, claiming its inability to keep up with demand for its G4 processor to be "a great endorsement" for the new chip.

"The product is a complex one to build, and we have to work through a number of issues and design changes in a short amount of time," the statement explained.

Apple has received orders for 150,000 Power Mac G4s since the product was unveiled late last month at the Seybold publishing conference in San Francisco.

Apple hopes to meet the orders backlog "early in the coming quarter", interim CEO Steve Jobs said in a statement.