Handsets will launch a week later on October 29.
According to The Verge's sources, Windows Phone 8 pre-orders from AT&T will commence on October 21, despite handsets being not expected to launch until October 29.
The carrier will apparently begin taking pre-orders on the HTC 8X, Nokia's Lumia 920, Samsung's Ativ Smart PC and the Asus Vivo Tab RT on the aforementioned date.
AT&T will sell both Nokia's Lumia 920 and 820 Windows Phone devices, while the latter will also be available from other carriers, including T-Mobile. The 920, however, will be an exclusive handset to AT&T.
As for Microsoft's HTC smartphones, AT&T is planning to sell the HTC One X+, One VX and Windows Phone 8X.
Windows 8 is due for a release on October 26, alongside the launch of Microsoft's Surface tablet.