Fisichella is worried about the safety issues of rising speeds

The Sauber driver says Sunday's Canadian Grand Prix, already renowned for heavy brake wear, could prove problematic as speeds continue to rise.

"It is very critical this year for the brakes," Fisichella said.

"The lap times are very quick, they did big improvements on the tyre development and I think that Formula One is now maybe a bit too quick."

Fisichella said that the increase in speeds caused by the improvement in tyre performance had made it difficult to prevent the brakes from overheating.

"We run with very high temperatures front and rear and it is quite difficult to find good brake ducts for the cooling," the Italian said.

A tyre war between Bridgestone and Michelin has led to rapid improvements in performance since 2001.

We have already had problems Kimi Raikkonen

Canada's Circuit Gilles Villeneuve is notorious for brake failures, which usually occur when brake discs overheat under heavy braking.

Because of the track lay-out - which features lots of long straights requiring the cars to run at the highest possible speeds - teams will be running their cars in low-downforce set-up.

The combination of straights followed by slow corners that require heavy braking intensifies the problems already being suffered by F1 teams this season.

And there are fears that warm temperatures could increase the risk of problems.

Any breakage could be catastrophic and Finnish McLaren-Mercedes driver Kimi Raikkonen said: "We're going three or four seconds quicker than last year so it's going to be harder for brakes and for all the other parts too.

"All the teams have been working to try to improve their situation but we have already had problems this year on circuits where we didn't used to have problems and coming here is going to be difficult."