Raikkonen is looking for his first victory in Monza
Kimi Raikkonen celebrated signing a new Ferrari contract by setting the fastest time in Friday practice at the Italian Grand Prix.
The world champion, whose deal has been extended by a year to the end of 2010, narrowly beat BMW Sauber's Robert Kubica in a largely dry session.
As sunshine replaced the morning's torrential rain, the Finn beat Kubica by 0.070 seconds with a 1:23.861 lap.
Nick Heidfeld was third for BMW Sauber ahead of McLaren's Lewis Hamilton.
McLaren had been expected to have the edge over Ferrari at the high-speed Monza circuit because of the silver cars' greater ability to ride the kerbs, a vital characteristic at the historic track.
But Raikkonen appeared the most consistently competitive driver on Friday, emerging as the fastest man at various points throughout the 90-minute afternoon session.
His team-mate Felipe Massa, who is Ferrari's main title contender just two points behind Hamilton, was 0.386 secs off Raikkonen's pace in sixth place.
Both Hamilton and team-mate Heikki Kovalainen appeared to be on course to beat Raikkonen's time at the end of the session.
But after setting the pace for the first two-thirds of the lap, they both lost time in the final sector, which comprises two long straights and the demanding, high-speed Parabolica corner.
Hamilton ended up 0.122 secs slower than Raikkonen and just ahead of Williams driver Nico Rosberg.
Instead, Raikkonen underlined his form with a final lap that was just 0.02secs slower than his fastest.
The pace of the BMWs suggests that they may be able to challenge the top two teams in the race on Sunday.
Monza share similar characteristics to Montreal, where Kubica won in June.
His victory came as a result of a collision between Hamilton and Raikkonen in the pits, but BMW were closer to the top teams in Canada than they have been at any track since.
Friday's first practice session was rendered meaningless by a massive thunderstorm that soaked the circuit and flooded some of the garages and commentary booths.
Hamilton had not even bothered to leave the pits when light rain turned into a torrential downpour with 20 minutes of the session remaining.
That brought all the cars in to the pits and effectively ended the session.
In an echo of his performance in the wet British Grand Prix, Massa went off the track five times in his Ferrari and was slowest of the cars who did manage some flying laps.
The forecast is for more rain off and on during the weekend.
If there is a wet race, conditions will dramatically favour McLaren as the Ferrari's relatively light treatment of its tyres means they struggle in mixed conditions compared to their rivals.
Second practice times in Monza:
1. Kimi Raikkonen (Fin) Ferrari 1m 23.861
2. Robert Kubica (Pol) BMW Sauber 1:23.931
3. Nick Heidfeld (Ger) BMW Sauber 1:23.947
4. Lewis Hamilton (GB) McLaren-Mercedes 1:23.983
5. Nico Rosberg (Ger) Williams-Toyota 1:24.110
6. Felipe Massa (Brz) Ferrari 1:24.247
7. Heikki Kovalainen (Fin) McLaren-Mercedes 1:24.365
8. Mark Webber (Aus) Red Bull-Renault 1:24.521
9. Adrian Sutil (Ger) Force India-Ferrari 1:24.669
10. Sebastian Vettel (Ger) Toro Rosso-Ferrari 1:24.773
11. David Coulthard (GB) Red Bull-Renault 1:25.100
12. Sebastien Bourdais (Fra) Toro Rosso-Ferrari 1:25.192
13. Giancarlo Fisichella (Ita) Force India-Ferrari 1:25.204
14. Rubens Barrichello (Brzl) Honda 1:25.296
15. Jenson Button (GB) Honda 1:25.309
16. Kazuki Nakajima (Jpn) Williams-Toyota 1:25.330
17. Timo Glock (Ger) Toyota 1:25.397
18. Fernando Alonso (Spa) Renault 1:25.481
19. Jarno Trulli (Ita) Toyota 1:25.753
20. Nelson Piquet (Brz) Renault 1:26.195
First practice times:
1. Adrian Sutil (Ger) Force India- Ferrari 1m 32.842s
2. Rubens Barrichello (Brz) Honda 1:33.428
3. Giancarlo Fisichella (Ita) Force India-Ferrari 1:33.695
4. Timo Glock (Ger) Toyota 1:36.800
5. Nico Rosberg (Ger) Williams-Toyota 1:36.900
6. Fernando Alonso (Spn) Renault 1:36.965
7. Sebastien Bourdais (Fra) Toro Rosso-Ferrari 1:37.142
8. Jarno Trulli (Ita) Toyota 1:37.214
9. Kimi Raikkonen (Fin) Ferrari 1:37.392
10. Sebastian Vettel (Ger) Toro Rosso-Ferrari 1:37.754
11. Nelson Piquet (Brz) Renault 1:38.057
12. David Coulthard (GB) Red Bull-Renault 1:38.303
13. Jenson Button (GB) Honda 1:39.062
14. Felipe Massa (Brz) Ferrari 1:40.233
15. Nick Heidfeld (Ger) BMW Sauber
16. Kazuki Nakajima (Jpn) Williams-Toyota
17. Robert Kubica (Pol) BMW Sauber
18. Heikki Kovalainen (Fin) McLaren-Mercedes
19. Mark Webber (Aus) Red Bull-Renault
20. Lewis Hamilton (GB) McLaren-Mercedes