US mobile operator AT&T is to allow users of Android-based smartphones to download apps from the new Amazon Appstore, in what appears a change of policy from the operator’s previous stance of not allowing access to third-party Android stores. Responding to a question from Engadget, AT&T confirmed the change: “We’re working to give our Android customers access to third-party application stores. This requires updates to our systems and finalizing arrangements with Amazon. We will share more info with our customers in the near future.”

The change of attitude from AT&T first surfaced via a statement from Angry Birds developer Rovio on Facebook. Rovio is offering Angry Birds Rio exclusively to Android users via Amazon’s new store. If AT&T does not negotiate access with Amazon then its users will miss out on this latest title in the hugely popular game.

The Angry Birds exclusive was a key attraction for Amazon’s Android store which launched earlier this week. It is only exclusive for a limited time. AT&T’s announcement is an early sign of how Amazon’s new store has the potential to cause disruption in the apps market.