BMW's [Images] Nick Heidfeld [Images] believes Formula One's return to Europe at Imola next week could force a re-writing of the early-season form book.

"We can expect many teams to arrive for the start of the European season with revised cars, which might well bring about another shift in the balance of power," the German driver said in an interview issued by the team on Wednesday.

"We'll be lining up with a modified rear section and a new front wing," he said. "Indeed, we had already introduced new aerodynamic elements for the race in Australia and the improvement was noticeable straightaway.

"Our aim is to make aerodynamic modifications of varying degrees before each Grand Prix."

Heidfeld finished fourth in the April 2 Australian Grand Prix, with Canadian Jacques Villeneuve a strong sixth, to send the new BMW Sauber team fifth in the championship.

BMW bought Swiss-based Sauber last year after winning 10 races in six seasons as engine partners to former champions Williams.

"Before the season started I said that we shouldn't put too much pressure on ourselves, but at the same time we needed to be sure that we were heading in the right direction and could maintain a consistent rate of improvement," said Heidfeld.

"That's certainly been the case in the first three races."

Because of the distance involved, with the first three races in quick succession in Bahrain, Malaysia and Australia, teams have been unable to make major changes to their cars until returning to their European home territory.

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