Microsoft is delaying the rollout of the beta of its Longhorn operating system until early next year in order to focus on improving security in its Windows XP Service Pack 2 (SP2).

The beta of Longhorn - the successor to Windows XP - was supposed to be distributed before the end of this year, but has now been moved back because its developers have been shifted onto the SP2 project.

The move is likely to delay the commercial rollout of Longhorn, which Microsoft said would only be released once beta trial customer feedback had been incorporated into the product.

"Windows XP Service Pack 2, due later this year, is a key component of Microsoft's commitment to helping improve security for our customers," said a company spokeswoman.

"To ensure SP2 delivers on customers' needs, Microsoft dedicated extensive resources to its development, and some of those resources were reallocated from Longhorn to SP2."

Microsoft plans major security enhancements to its Windows XP SP2 release, due later this year.

The product will include firewall enhancements and more secure email and instant messaging. A new Windows Security Centre feature will allow users to monitor information on firewalls, automatic updates and third-party antivirus software.

In 2001, Microsoft spoke about releasing Longhorn in late 2004, but then said it was likely to delay the release until the second half of 2005.

At Microsoft's developer conference in October 2003, the implication was that Longhorn would be more likely to ship in 2006, again hinted at by Bill Gates this week at a conference held by analyst Gartner.

Yet Gartner predicts that the delay could be even longer, with the new operating system not shipping until 2007.

"Longhorn will ultimately be delivered when we've incorporated customer and partner feedback from the beta process and the code meets the quality standards our customers require," said the Microsoft spokeswoman.