Sebastian Vettel fired a warning to his rivals in final practice for the Canadian Grand Prix, the Red Bull driver setting the pace ahead of qualifying in Montreal.
The World Champion finished with a time of 1m13.381s to outpace Ferrari's Fernando Alonso by over three tenths in a session that finished a few seconds ahead of scheduled because of a crash by Pedro de la Rosa.
Nico Rosberg was third quickest for Mercedes, with Ferrari's Felipe Massa in fourth and the McLarens of Jenson Button and Lewis Hamilton in fifth and sixth.
De la Rosa, replacing the unwell Sergio Perez at Sauber, caused a red flag with less than a minute left after crashing against the well at the exit of Turn 9. The session was not restarted.
Mark Webber had another disappointing session after being hit by KERS issues, the Australian unable to leave his garage as mechanics continued to work on his car.
The Mercedes duo were the early pacesetters, with Rosberg shooting to the top of the times with a lap of 1m15.034s. He was followed by teammate Michael Schumacher initially, but Button, Petrov and then more drivers relegated the German down to seventh with some 40 minutes left.
Button moved to first place minutes later when he became the first man to lap in the 1m14s, but he didn't last long there, as Vettel showed his speed and stopped the clock on 1m14.126s with the soft rubber. Rosberg also made a significant improvement to place himself in second less than a tenth behind the World Champion.
On the following lap, Rosberg moved to the top again thanks to another run with his super-softs, the Mercedes man lapping in the 1m13s for the first time this weekend.
Alonso went for his first qualifying simulation with 17 minutes to go but, despite using super soft tyres, the Spaniard could not beat Rosberg's time. He came as close as possible, however, the Ferrari driver setting the exact same time as the Mercedes racer - 1m13.919s.
Alonso completed a second flying lap with the same set of super-softs, but was nearly a tenth of a second slower, like teammate Massa just seconds earlier. On his third lap, however, the Spanish driver outpaced Rosberg with a lap of 1m13.701s as the sky become very dark and threatened rain for qualifying.
Vettel started his first run on super softs with five minutes remaining, but the German aborted his first attempt because of traffic. On the second lap he moved to first place, however, lapping over three tenths quicker than Alonso.
Pos Driver Team Time Laps
1. Sebastian Vettel Red Bull-Renault 1m13.381s 21
2. Fernando Alonso Ferrari 1m13.701s + 0.320 21
3. Nico Rosberg Mercedes 1m13.919s + 0.538 29
4. Felipe Massa Ferrari 1m13.956s + 0.575 20
5. Jenson Button McLaren-Mercedes 1m14.335s + 0.954 18
6. Lewis Hamilton McLaren-Mercedes 1m14.469s + 1.088 16
7. Michael Schumacher Mercedes 1m14.488s + 1.107 23
8. Vitaly Petrov Renault 1m14.917s + 1.536 23
9. Adrian Sutil Force India-Mercedes 1m15.217s + 1.836 18
10. Paul di Resta Force India-Mercedes 1m15.243s + 1.862 17
11. Pastor Maldonado Williams-Cosworth 1m15.312s + 1.931 19
12. Nick Heidfeld Renault 1m15.350s + 1.969 22
13. Sebastien Buemi Toro Rosso-Ferrari 1m16.138s + 2.757 17
14. Jaime Alguersuari Toro Rosso-Ferrari 1m16.145s + 2.764 19
15. Kamui Kobayashi Sauber-Ferrari 1m16.236s + 2.855 21
16. Rubens Barrichello Williams-Cosworth 1m16.438s + 3.057 21
17. Pedro de la Rosa Sauber-Ferrari 1m16.706s + 3.325 22
18. Heikki Kovalainen Lotus-Renault 1m17.093s + 3.712 21
19. Jarno Trulli Lotus-Renault 1m17.523s + 4.142 24
20. Tonio Liuzzi HRT-Cosworth 1m18.910s + 5.529 20
21. Timo Glock Virgin-Cosworth 1m19.073s + 5.692 19
22. Narain Karthikeyan HRT-Cosworth 1m19.213s + 5.832 22
23. Jerome D'Ambrosio Virgin-Cosworth 1m20.475s + 7.094 19
24. Mark Webber Red Bull-Renault No time
All Timing Unofficial