Apple has pushed back the launch of its next operating system OS 10.5 codenamed Leopard until October.

The company, who had announced that the new OS would be available this Spring is citing development issues on its new mobile phone, the iPhone, as the cause of delay.

"Life often presents trade-offs, and in this case we’re sure we’ve made the right ones", Apple said in a statement.

According to the company the main reason for the delay is because it had to pull off key personal to make sure the iPhone made its June launch date in the US.

"iPhone contains the most sophisticated software ever shipped on a mobile device, and finishing it on time has not come without a price — we had to borrow some key software engineering and QA resources from our Mac OS X team, and as a result we will not be able to release Leopard at our Worldwide Developers Conference in early June as planned."

Apple says that it plans to show developers attending its WWDC in June "a near final version of Leopard" and release a beta copy at the same time for developers to take home so they can do their final testing.

However Apple still hasn't confirmed a specific launch date in June in the US. In the UK Apple is citing that UK customers should get the phone by Christmas, however hasn't actually confirmed a launch date.