Red Bull's Sebastian Vettel has shown his intent ahead of the United States Grand Prix on Sunday by clocking the fastest time in the first practice in Austin, Texas.

McLaren driver Lewis Hamilton, who sped off the track to avoid clashing with Michael Schumacher on the exit of turn nine, looked poised to take the best time with 12 minutes left to go in the practice.

Despite his impressive session, Vettel, who initially seemed to be struggling with the handles of his car, managed to whip around the track and finish the circuit 1.4 seconds faster than the Brit.

Ferrari's Fernando Alonso, who is Vettel's biggest challenger for the title, clocked the third quickest time, which was 2.2 seconds behind the Red Bull driver, who currently leads by 10 points in the drivers' rankings with two races left to go in the season.

First practice standings:

1. Sebastian Vettel (Red Bull) - 1:38.125
2. Lewis Hamilton (McLaren) - 1:39.543
3. Fernando Alonso (Ferrari) - 1:40.337
4. Jenson Button (McLaren) - 1:40.528
5. Mark Webber (Red Bull) - 1:40.650
6. Felipe Massa (Ferrari) - 1:40.966
7. Nico Hulkenberg (Force India) - 1:41.023
8. Kamui Kobayashi (Sauber) - 1:41.036
9. Nico Rosberg (Mercedes) - 1:41.159
10. Sergio Perez (Sauber) - 1:41.473
11. Paul Di Resta (Force India) - 1:41.783
12. Daniel Ricciardo (Toro Rosso) - 1:41.825
13. Jean-Eric Vergne (Toro Rosso) - 1:41.833
14. Kimi Raikkonen (Lotus) - 1:41.880
15. Romain Grosjean (Lotus) - 1:41.998
16. Pastor Maldonado (Williams) - 1:42.539
17. Michael Schumacher (Mercedes) - 1:42.588
18. Charles Pic (Marussia) - 1:43.288
19. Heikki Kovalainen (Caterham) - 1:43.443
20. Vitaly Petrov (Caterham) - 1:43.522
21. Timo Glock - (Marussia) - 1:44.464
22. Bruno Senna (Williams) - 1:44.548
23. Pedro de la Rosa (HRT) - 1:46.917
24. Ma Qinghua (HRT) - 1:48.559