We knew that AT&T was planning to turn on its LTE service in a number of new regions before the end of the year, and it appears one city has been given the green light: Seattle. A trusted source tells us that the service has in fact gone live in the city, with a reader also reporting that they've recently seen the service sporadically spring to life on their own LTE device. In several tests, the reader saw download speeds range between 17.1Mbps and 22Mbps.

The move happens just days before the release of the iPhone 5, a phone that will no doubt prove to be one of AT&T's most popular LTE devices. With the carrier racing to catch up with Verizon's own LTE rollout — and true 4G being one of the main selling points of Apple's latest phone — LTE availability will no doubt be a deciding factor for many consumers deciding which carrier they'd like to sign up with for the next two years.

Update: Seattle confirmed, and Detroit and Portland just announced too.

Update 2: We're hearing more reports from readers that AT&T LTE service has also come on in Pittsburgh, Philadelphia, and Cincinnati, as well.

Update 3: They just keep on coming in. Now Honolulu has been lit up, and Pittsburgh has been confirmed. Birmingham and Memphis, meanwhile, got LTE yesterday.

Thanks, BumpyClock!