Porsche wants the Cayenne hybrid to require just 8.9 liters of petrol per 100 kilometers, compared with the 12.9 liters its conventional Cayenne guzzles.

Europe's automotive industry is facing ever more stringent carbon dioxide (CO2) guidelines from regulators eager to curb greenhouse gas emissions.

The European Commission plans new rules by mid-2008 to reduce CO2 emissions from new passenger cars to an average 130 grams of C02 per km by 2012 through improved engine technology.

By comparison, Cayennes now exhale as much as 320 to 378 grams per km depending on the model, according to data from German automotive market researcher DAT.

Porsche is working with Volkswagen AG and Audi AG to develop hybrid powertrains that capture energy from braking. A battery then drives an electric motor alongside a petrol engine.

The so-called parallel-full hybrid lets the vehicle drive on electric power alone at speeds up to 120 km per hour, with the combustion engine first taking over at higher speeds.

Porsche said it would offer a hybrid version of its planned fourth model, the four-door Panamera coupe, but it does not plan to do so for either its Boxster/Cayman model line or its 911 sports cars.