HERNDON, VA - Audi's march toward becoming the leading premium brand by 2015 will include the new A5 Sportback, but with one caveat: The car has not been approved for launch in the U.S., Audi says.

Why no U.S.-bound A5 Sportback? According to Motor Trend, it's largely because the production version of the Sportback concept from the Detroit Auto Show -- to be called the A7 -- will be coming instead. Billed as a Mercedes-Benz CLS-fighter, the A7 is somewhat similar in mission to the A5 Sportback, but bigger and arguably more luxurious. An A5 Sportback on top of the A3, A4, A5 Coupe/Cabrio, A6, A7, and A8 would likely be overkill.

So far, Audi has only released a design sketch and a teaser photo of the car's rear three-quarter view (shown below). The A5 Sportback appears to draw from both the A4 sedan and the A5 coupe. The shape of the taillights are reminiscent of the A5, yet the LED pattern more closely resembles the A4.

The A5 Sportback's rear three quarter windows fill out the side view well and actually remind us of the rear windows on the Honda Accord coupe.

With the launch of the A5 Sportback limited to markets outside the U.S., powertrains will roughly follow those offered on the A5 coupe and the car will come with all the latest tech features found on its sibling. From the start, the A5 Sportback will be available with the 2.0L 211-hp turbocharged four-cylinder, that same engine available with quattro, as well as the 3.2L 265-hp V-6 with or without quattro. Don't forget about diesel. The A5 Sportback will also be available with a choice of 2.0L, 2.7L, and 3.0L TDI diesels; the first and third engines can be optioned with quattro. Audi would be stupid not to offer a low-volume S5 Sportback as a high-performance halo vehicle for the new model, and we suspect they will.

Audi says the A5 Sportback will feature 17.0 cu-ft of cargo space with the rear seats up and 34.6 cu-ft with them folded down. The A5 Sportback will begin arriving in dealerships this September after its debut at the 2009 Frankfurt Motor Show.