Nokia has made the rumors official today, as it unveiled the new Lumia 900 Windows Phone smartphone. The gadget will be a 4G LTE device and it’s coming to AT&T’s network.

“The Nokia Lumia 900 allows data downloads up to 50Mbps on AT&T’s 4G LTE network,” Nokia boasted in a press release. Customers who can’t access LTE will have to struggle along with HSPA+, which is theoretically capable of 21Mbps.

The Windows Mango Phone, Nokia Lumia 900 has a 4.3-inch AMOLED ClearBlack Display for rich, bright images both indoors and out, faster connection speeds based on cutting-edge 4G LTE technology, and a long-lasting 1830 mAh battery for enjoying content all day.

Some other specs: the Lumia 900 has a 512MB of RAM; 16GB internal memory plus Microsoft’s SkyDrive cloud storage; and weighs 5.6 ounces. In addition to an 8-megapixel camera with dual LED flash, the Lumia 900 will support “hi-res video capture for 720p/30fps action footage,” and has a second, front-facing camera for video calls.

As usual, Nokia apps will be provided with the phone to differentiate the device from other WP phones. The Nokia Lumia 900 will be available in black and blue (cyan) on AT&T later this year. Pricing has not been announced.

On a side note, The Nokia Lumia 710, which we reported, is coming to T-Mobile on January 11. No words on Lumia 800 release.