MELBOURNE (AFP) - - German Nico Rosberg offered Williams-Toyota the tantalising prospect of breaking its long Grand Prix win-drought with the fastest times in Friday's practice sessions in Melbourne.

Rosberg topped the time charts in both sessions, finishing the day with a fastest lap time of one minute 26.053 seconds ahead of this weekend's highly anticipated Australian Formula One season-opener.

The 23-year-old German was 0.104secs superior to Brazilian Rubens Barrichello, behind the wheel of the new Brawn GP car.

"The car is well-balanced all round the track, but seems even more so here than in any other place," Rosberg said ahead of Saturday qualifying.

"After a winter of testing, it's good to get out on a new fresh track and we seem to be in a better position than we thought."

While Rosberg gave Williams much encouragement ahead of Sunday's curtain-raiser, championship heavyweights Ferrari and McLaren endured a difficult first day on the Melbourne street circuit.

The Ferrari duo of Felipe Massa and Kimi Raikkonen were 10th and 11th fastest in the second session, while world champion Lewis Hamilton of McLaren came home a lowly 18th place out of 20, 1.76secs adrift of Rosberg's best time.

"We are more or less okay with the (car's) set-up, although there is still room to improve the performance," Massa said.

"Tomorrow, with everyone on the same fuel load, we will see what the situation is."

The teams fully utilised the opportunity to get in maximum laps in the three-hour practice, with new regulations not permitting further testing during the season.

Williams and two other teams, Brawn GP and Toyota, were the subject of protests from rival teams over the official scrutineering of their cars' rear diffusers, which FIA stewards late Thursday cleared to race.

Barrichello, in his 17th season and lining up for his 269th GP this weekend, gave promise of better things ahead for debutants Brawn GP, clocking a best lap of 1:26.157.

"To be in Melbourne is a real achievement for the team and despite the limited testing time we were able to do before the race, we have proved that we have a competitive car," Barrichello said.

Briton Jenson Button further underlined Brawn's impressive winter testing performances, coming fifth fastest in 1:26.374.

"We had a good first day of practice and the long-run performance looks competitive, particularly on the harder tyre," Button said.

Toyota's Jarno Trulli (1:26.350) and Australia's Red Bull racer Mark Webber (1:26.370), who is recovering from a broken leg, were third and fourth quickest in the second session.

Renault's former two-time world champion Fernando Alonso of Spain was 12th fastest in 1:27.232.

"We now have lots of valuable information and we will go over that this evening," Alonso said.

"We are missing some grip but we have some ideas about how we can overcome these issues, so I'm still confident.

"We should deliver a better performance tomorrow."

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