Ferrari's Fernando Alonso beat Red bull's Sebastian Vettel in final practice at the Bahrain Grand Prix.
The Spaniard was 0.101 seconds quicker than the world champion, who did not complete a flying lap on the faster of the two tyre options.
Vettel's team-mate Mark Webber was third fastest, 0.133secs behind Alonso, ahead of Lotus's Kimi Raikkonen.
Mercedes driver Lewis Hamilton was fifth as 0.5secs separated the top nine.
Hamilton toured back to the pits at the end of the session with a tyre and suspension failure, which left the rear tyre at an angle of 45 degrees.
Pirelli admitted that tyre failure was the cause, which led to the Mercedes' broken suspension and also damaged the gearbox. The team has since taken a five-place grid penalty as a result of fitting a new gearbox to Hamilton's car.
Lotus's Romain Grosjean was sixth, ahead of the Force Indias of Adrian Sutil and Paul di Resta, Mercedes' Nico Rosberg and Sauber's Nico Hulkenberg.
Ferrari's Felipe Massa was 11th ahead of McLaren's Jenson Button.
Alonso set the pace despite a spin earlier in the session. He lost control as he put the power down on the exit of Turn Two but was able to rejoin despite the car ending up in the gravel.
Vettel completed two-thirds of his flying lap on the softer 'medium' tyre before being held up by one of the Caterhams, at which the German demonstrated his exasperation by waving his hand out of the cockpit.
Vettel had been was just over 0.1secs slower than Alonso on his 'medium' run before hitting the traffic. The 'medium' will be the qualifying tyre.
BBC F1 technical analyst Gary Anderson said: "I wouldn't be surprised to see a Red Bull on pole, but it will be close with Alonso and Raikkonen."
The session, and the weekend's race, is taking place against the backdrop of continuing civil unrest in the Gulf state.
There were demonstrations against the ruling family attended by tens of thousands of people on Friday night.
But the race is being held under heavy security and, unlike last year, no F1 personnel have encountered any trouble unless they have gone out to the areas where the demonstrations and occasional riots are taking place.
1. Fernando Alonso (Spa) Ferrari 1min 33.247secs
2. Sebastian Vettel (Ger) Red Bull 1:33.348
3. Mark Webber (Aus) Red Bull 1:33.380
4. Kimi Raikkonen (Fin) Lotus 1:33.446
5. Lewis Hamilton (GB) Mercedes 1:33.455
6. Romain Grosjean (Fra) Lotus 1:33.464
7. Adrian Sutil (Ger) Force India 1:33.596
8. Paul Di Resta (GB) Force India 1:33.700
9. Nico Rosberg (Ger) Mercedes 1:33.764
10. Nico Hulkenberg (Ger) Sauber 1:33.922
11. Felipe Massa (Brz) Ferrari 1:33.949
12. Jenson Button (GB) McLaren :34.117
13. Sergio Perez (Mex) McLaren 1:34.282
14. Daniel Ricciardo (Aus) Toro Rosso 1:34.577
15. Valtteri Bottas (Fin) Williams 1:34.611
16. Jean-Eric Vergne (Fra) Toro Rosso 1:34.678
17. Pastor Maldonado (Ven) Williams 1:34.833
18. Charles Pic (Fra) Caterham 1:35.816
19. Jules Bianchi (Fra) Marussia 1:36.731
20. Giedo van der Garde (Ned) Caterham 1:36.939
21. Max Chilton (GB) Marussia 1:37.630
22. Esteban Gutierrez (Mex) Sauber 1:39.592