Auto industry sources told the German news agency that some 330,000 cars made by German manufacturers and more than 2 million imported cars wouldn't be able to run on the E-10 gasoline. Environment Minister Sigmar Gabriel told the Stuttgarter Nachrichten newspaper he would annul a government decree for the fuel if more than 1 million vehicles would be negatively affected.

The law would require regular gasoline be mixed with 10 percent ethanol by next year. The ratio would rise to 17 percent by 2020.

ADAC, Germany's central motoring club, is worried about damage to German cars and has called for the introduction of E-10 to be delayed by 2012. Greenpeace, meanwhile, is concerned that South American rain forests are being destroyed to produce the soy oil in the gasoline, Der Spiegel said.