In a rare admission of fallibility, Apple has delayed its next-generation operating system to ensure the timely release of the highly anticipated iPhone.

Leopard, the latest version of the Mac OS X line, will now be pushed back until October, from June. Analysts expect the move to hit Apple's software revenues by about $150 million this year and said there could be a knock-on effect on sales of its Mac computers.

The US debut of the iPhone, first unveiled in January and regarded as by far the more important product, is still slated for June, but Leopard engineers will be pulled onto the project to ensure it meets that deadline, Apple said. The news follows suggestions from people who have seen iPhone prototypes that the device is still far from ready.

The decision to divert resources to the iPhone underscores the expectation attached to Apple's first foray into the mobile sector. David Bailey, the Goldman Sachs analyst, said: "Although the push out of Leopard is not ideal, we view iPhone as the driver of the next leg to the Apple growth story."

The admission from Steve Jobs, the Apple chief executive, that "life often presents trade-offs" stands askance to the military precision with which Apple usually unveils new products. The company prides itself on keeping launches secret until the last minute, a tactic that feeds a fierce rumour mill and lifts hype.

The Leopard delay, however, is Apple's second in four months and will raise speculation that the group risks losing its legendary cool as it faces new competitors in new markets.

Apple TV, a device that streams video from computers to TV's and sets Apple against established set-top box makers such as Cisco's Scientific-Atlanta, was nudged back from February to March 21. The company has also drawn criticism in recent years for releasing versions of its iPod music players that were not robust enough.

Poor battery life - thought to be a problem on iPhone prototypes - has also plagued the iPod.

The glitch to Leopard, the sixth major upgrade to Mac OS X since 2001, will be all the more galling for Apple after the jibes it angled at Microsoft when Vista, its rival operating system, was put back two years.

Stuart Miles, the editor www.pocket-lint.co.uk, the technology site, said: "Market pressures and the fear of leaks has forced Apple to take a different approach with the iPhone. The looming deadline in the US clearly seems to be taking its toll."

Apple will ship two versions of the iPhone - a 4-gigabyte model for $499 and an 8-gigabyte one for $599. It will initially be available in the US through AT&T's Cingular Wireless network. It will be sold in Europe later this year and in Asia in 2008.

Apple has said it hopes to sell 10 million units in 2008, a total that would represent about 1 per cent of the mobile market.

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