Amazon's upcoming smartphone will be exclusive to AT&T, according to The Wall Street Journal. The e-commerce giant is widely expected to introduce its first ever smartphone at a media event tomorrow, building on its Kindle Fire line of Android tablets. Amazon already has a relationship with AT&T; the carrier provides wireless service to its tablets and e-readers, but securing an exclusive deal with Amazon for its smartphone would be a major extension of that partnership. It's unclear whether Amazon will also offer the smartphone through its online store SIM-free or if it will truly be limited to AT&T customers, but regardless, the majority of potential buyers are unlikely to buy a phone without a contract.

Although the major players in the smartphone industry now offer their phones across all of the larger carriers in the US, it's not uncommon for exclusive deals to be signed for new entrants to the market. Nokia's return to the US with its Lumia range launched exclusively on AT&T, and the company has continued to bring its "hero" devices to the carrier first. While the exact details of the deal are unlikely to ever be made public, partnering with a single carrier can be a good way to lower the cost of launching a phone: marketing costs are shared, reducing the risk for the manufacturer. We'll find out if The Wall Street Journal's inside sources are correct tomorrow, but in the meantime you can find out everything you need to know about Amazon's new smartphone here.