Microsoft said Tuesday that it has delayed an update to its Windows Server software as well as the first version of Windows to support 64-bit x86 chips such as Advanced Micro Device's Athlon 64.

The software maker said Windows Server 2003 Service Pack 1, Windows Server 2003 for 64-bit Extended Systems and Windows XP 64-bit Edition for 64-bit Extended Systems will all be pushed back until the first half of next year. All three products, which are being developed together, were slated to ship by the end of this year.

The move is a blow to AMD, which has had its 64-bit desktop and server chips on the market for some time and has been waiting for a version of Windows that can take advantage of their capabilities. Intel has also said it will have chips that support the 64-bit extensions to the existing Pentium architecture, known as x86. There is already a version of Windows that supports Intel's 64-bit Itanium architecture, which uses an entirely separate instruction set than x86 chips.

"As is the case with all Microsoft product schedules, the development cycle is driven by quality with a focus on the needs of our customers, rather than an arbitrary date," Microsoft said in a statement.