Red Bull duo Sebastian Vettel and Mark Webber have gone fastest in the second practice session ahead of Sunday's United States Grand Prix in Austin, Texas.
The German, who leads the championship, continued his pace from the first session, when he finished ahead of Lewis Hamilton's McLaren.
Fernando Alonso once again came home third fastest, while Hamilton, Jenson Button and Felipe Massa trailed.
The end result means that Ferrari, McLaren and Red Bull have posted the top six times for in both sessions.
Nico Rosberg, Bruno Senna, Kamui Kobayashi and Michael Schumacher complete the top 10. Kimi Raikkonen, winner of the Abu Dhabi Grand Prix, could only finish 11th.
Second practice standings:
1. Sebastian Vettel (Red Bull)
2. Mark Webber (Red Bull)
3. Fernando Alonso (Ferrari)
4. Lewis Hamilton (McLaren)
5. Jenson Button (McLaren)
6. Felipe Massa (Ferrari)
7. Nico Rosberg (Mercedes)
8. Bruno Senna (Williams)
9. Kamui Kobayashi (Sauber)
10. Michael Schumacher (Mercedes)
11. Kimi Raikkonen (Lotus)
12. Pastor Maldonado (Williams)
13. Romain Grosjean (Lotus)
14. Sergio Perez (Sauber)
15. Danniel Ricciardo (Toro Rosso)
16. Jean-Eric Vergne (Toro Rosso)
17. Nico Hulkenberg (Force India)
18. Paul di Resta (Force India)
19. Heiki Kovalainen (Caterham)
20. Timo Glock (Marussia)
21. Vitaly Petrov (Caterham)
22. Charles Pic (Marussia)
23. Pedro de la Rosa (HRT)
24. Charles Pic (Marussia)
25. Narain Karthikeyan (HRT)
