US operator AT&T has today added to the iPhone 5 buzz with the announcement that the new phone has overtaken the iPhone 4S as its fastest selling Apple device, fuelling reports that the iPhone 5 has become Apple’s fastest selling smartphone ever.

Speaking with AllThingsD, AT&T shared the news ahead of the iPhone 5′s general release on Friday, September 21, when preorders made via the Apple website and the US operator will begin to ship.

Last Friday, it only took an hour for Apple’s website to reflect shipping delays, with delivery estimates slipping to between ’2-3 weeks’ in all of the seven launch countries. AT&T appears to have ridden a similar wave, seeing more than 200,000 preorders over the last week.

In October 2011 — shortly after the iPhone 4S launch — AT&T announced that it had seen more than 200,000 preorders in 12 hours, making it the most successful launch in the device’s 4 year history. Today’s announcement means the company either topped that tally in a similar period of time or saw sustained demand for the iPhone 5 over the launch weekend.

Last week, we reported that initial shipments of iPhone 5 had sold out on all US carriers, including Verizon, AT&T and Sprint. Neither Verizon or Sprint have shared statements on their preorder sales.

Apple has also commented on iPhone 5 pre-sales:

“Pre-orders for iPhone 5 have been incredible. We’ve been completely blown away by the customer response.”

We can expect Apple to release launch figures in the next 24-48 hours. It seems almost certain that preorders will beat the initial 4 million sales the iPhone 4S achieved last year, not bad for a device many believe is boring.