The hatchback will return approximately 156 mpg in a mixed European cycle.

Audi has announced it will launch a plug-in hybrid version of the A3 Sportback sub-compact hatchback across the United States in 2015.Previewed by a thinly-veiled concept that bowed in Geneva earlier this year, the A3 Sportback e-tron will be powered by a heavily-modified 1.4-liter TFSI engine and a compact 100-horsepower electric motor integrated into a brand-new six-speed gearbox called e-S tronic. Combined, the two power sources will send 201 horsepower and 258 lb-ft. of torque to the front wheels.

The driver will be able to choose whether the car is running on gasoline, on electricity or on both by flicking a switch on the center console.

When driven conservatively, the e-tron will return 156 mpg in a mixed European cycle and emits just 35 grams of CO2 per kilometer. Alternatively, the hatchback will be able to operate on electricity alone for 31 miles at speeds of up to 80 mph.

If fuel economy is not a concern, the electric motor will provide a power boost that will enable the e-tron to reach 62 mph from a stop in 7.2 seconds and reach a top speed of 137 mph.

Audi will publish a full set of details about the 2015 A3 e-tron closer to its on-sale date. Pricing information is not available, but expect it to be priced near the top of the A3 lineup.

The e-tron will be the only A3 hatchback sold in the United States. All other models - including diesel-burning TDI-badged variants and 296-horsepower S versions - will only be available as a four-door sedan.