Championship leader Fernando Alonso put Formula One pacesetters Renault on provisional pole position for the Bahrain Grand Prix in Manama on Saturday.
The young Spaniard, who will be chasing the team's third win in as many races this season and his second in a row on Sunday, lapped the desert Sakhir circuit in one minute 29.848 seconds.
Italian Jarno Trulli was second for Toyota, 0.145 of a second slower, and on course for his third front row start in succession.
With track temperatures of 54 degrees celsius, seven times world champion Michael Schumacher launched flagging Ferrari's fightback after two disappointing races in last year's car with third place in the new F2005.
The decisive final session is on Sunday, with grid positions decided by aggregate times.
Schumacher's Brazilian team mate Rubens Barrichello, limping through the session with a patched-up gearbox after a failure on Friday forced him to miss three practice sessions, was 15th.
Ferrari are flying out a new gearbox for his car and will have about two hours to install it on Sunday morning before the final qualifying.
Germany's Nick Heidfeld was fourth quickest for Williams, ahead of Italian Giancarlo Fisichella in the second Renault and Australian Mark Webber for Williams.
Spaniard Pedro de la Rosa, replacing the injured Colombian Juan Pablo Montoya at McLaren, was ninth fastest.
Results of the first qualifying session:
1. Fernando Alonso (Spain) Renault 1:29.848
2. Jarno Trulli (Italy) Toyota 1:29.993
3. Michael Schumacher (Germany) Ferrari 1:30.237
4. Nick Heidfeld (Germany) Williams - BMW 1:30.390
5. Giancarlo Fisichella (Italy) Renault 1:30.445
6. Mark Webber (Australia) Williams - BMW 1:30.592
7. Kimi Raeikkoenen (Finland) McLaren - Mercedes 1:30.594
8. Christian Klien (Austria) Red-Bull - Cosworth 1:30.646
9. Pedro de la Rosa (Spain) McLaren - Mercedes 1:30.725
10. Felipe Massa (Brazil) Sauber - Petronas 1:30.933
11. Ralf Schumacher (Germany) Toyota 1:30.952
12. Jenson Button (Britain) BAR - Honda 1:30.957
13. Takuma Sato (Japan) BAR - Honda 1:31.113
14. David Coulthard (Britain) Red-Bull - Cosworth 1:31.211
15. Rubens Barrichello (Brazil) Ferrari 1:31.826
16. Jacques Villeneuve (Canada) Sauber - Petronas 1:32.318
17. Narain Karthikeyan (India) Jordan - Toyota 1:33.190
18. Tiago Monteiro (Portugal) Jordan - Toyota 1:33.424
19. Christijan Albers (Netherlands) Minardi - Cosworth 1:34.005
20. Patrick Friesacher (Austria) Minardi - Cosworth 1:34.848