Rubens struggles on opening day

The Brazilian ended the day only ninth fastest, almost three-quarters of a second slower than Schumacher's best time.

"It was a tough day for me with a few problems - even the radio was not working for a while!" said Barrichello. "We now have to look at the set-up of the car and I am confident that, after working tonight with my engineers, we will have a much better day tomorrow."

Technical director Ross Brawn confirmed: Michael made good progress with his car while Rubens was not quite so happy, particularly on the braking side, so we have some work to do tonight.

"However, it is pleasing to see that we look competitive in these hot conditions. Tyres are definitely going to be the key factor over the course of this weekend. The track temperature was very high today and we already have a strong indication of which type of tyre we want to race with here."

Schumacher added: "We worked well on the car and had clean runs, helped by the fact that right from the start of this morning's session, we had a good baseline in terms of car set-up. I am quite happy with the overall situation. I think today was a good preparation for tomorrow and Sunday's race, which I am looking forward to."