BMW-Sauber chief Mario Theissen is open to the formula one calendar expanding to a maximum of 20 races -- but only if the format for the actual grand prix weekend is restructured.

F1 chief executive Bernie Ecclestone suggested recently that five potential new hosts are ready to join the annual schedule, which at 18 races this year is set to dispense with the August break in 2009 and expand to 19 events in 2009.

Theissen, however, thinks 20 races is the absolute limit, providing in-season testing is further reduced.

The German has always thought real free testing at the grand prix venues, prior to the official weekend schedule, is a good compromise, rather than simply the recent increase to three hours of Friday practice.

"I think it would make sense, because we have all the material with us anyway," said Theissen, proposing that Fridays became all-day free test sessions.

But while F1 fans hungry for more action at grand prix weekends would be unlikely to complain, Theissen admits his proposal would also "have consequences" for support events like GP2.

"In my opinion 20 races is the limit -- provided the testing is reduced considerably," he said.

Source: GMM