ROME (AFP) -- Italian Prime Minister Silvio Berlusconi said Saturday that Germany is not giving any preferential treatment to Italian automaker Fiat (F.MI) in its takeover bid for General Motors' (GM) Opel unit.

"I can say that the German government is being totally impartial in the Fiat-Opel case," he said in an interview with T9 television channel.

German government officials said Friday that Berlin will decide next week which of three bidders is its preferred choice to take over Opel, but Canadian auto parts maker Magna International (MGA) is in pole position.

Meanwhile on Saturday, German Economy Minister Karl-Theodor zu Guttenberg said Fiat had improved its bid for a stake in the GM unit and had offered more details.

The final decision on Opel, as well as other units of GM's European operations, including Britain's Vauxhall and Sweden's Saab, lies with GM itself and the US government.

But Berlin has a major say as it has promised to sweeten any deal with loan guarantees, and last week it appeared that Canadian auto parts maker Magna International had made a more convincing offer.