Vettel fastest as Red Bull dominate Formula One practice

Vettel -- bidding for a fourth consecutive world drivers' crown -- posted the fastest times in both practice sessions, settling with a best of one minute 25.908 seconds in the afternoon to stake his claim for Sunday's Melbourne race.

Australian Mark Webber completed an emphatic one-two for the champion Red Bull team as main title rivals Ferrari and McLaren struggled.

Ferrari's Fernando Alonso, edged out by Vettel in last year's championship, finished 0.840 secs behind Vettel's fastest lap, while last season's Melbourne winner Jenson Button was well down in 11th place in his McLaren.

Team principal Martin Whitmarsh said McLaren were "struggling to understand" their new car and were lacking grip. He said it was "a tough day".

Vettel firmly eased doubts over Red Bull's performances in winter testing in Spain with his fast times as the Formula One season got underway.

Coupled with Webber's speed in the team's other car Red Bull threw down the gauntlet to their rivals that they have the early speed ahead of Saturday's qualifying for grid positions in the season opener.

Lewis Hamilton, driving for Mercedes, clocked the seventh best lap time of 1:26.772 before his session was finished when he ran off the circuit near the end.

German Nico Rosberg ran an encouraging third (1:26.322) for Mercedes but his afternoon session finished early with gearbox trouble.

Former world champion Kimi Raikkonen was fourth in a Lotus ahead of French teammate Romain Grosjean.