Ferrari fired a warning to title rivals Renault when Michael Schumacher's number two Felipe Massa set a scorching pace in Hungarian Grand Prix practice.
Massa's job is to finish ahead of Alonso, depriving him of points
The Brazilian's lap in the second session was 1.319secs faster than that of Schumacher's title rival Fernando Alonso of Renault, who was second.
But Massa did not beat a faster time set by McLaren's Kimi Raikkonen in the morning when conditions were different.
Over the two sessions, Schumacher was fourth fastest and Alonso seventh.
Renault are not using the "mass damper" system, the loss of which caused them major problems in the last race.
The team decided not to run it on their car after a series of communications from Formula One's governing body the FIA in the run up to the race.
In the second session, which started on a damp track, no driver was able to beat the 1:21.624 lap set by Raikkonen in the morning.
And several drivers lost control on the tight and twisty track, which is always slippery on the first day of a Grand Prix meeting.
Super Aguri's Sakon Yamamoto was the first to slip up, running wide at the fourth turn.
The times seem competitive, so I think we are on the right track
Test drivers Markus Winkelhock of Midland and Robert Doornbos of Red Bull followed suit at other corners later on, as did Fisichella and Toro Rosso's Vitantonio Liuzzi as the track began to dry and the lap times came down.
Alonso played down the difference in pace between Massa and himself in the afternoon session.
"It was a good start to the weekend for me," the world champion said.
"The conditions were very low grip and that meant the car balance was quite inconsistent, but we managed to do our normal programme, get a feel for the tyre performance and start making some set-up changes.
"I was having some problems with the rear end to begin with, but we managed to calm it down during the session and we will carry on working in that direction.
"The times seem competitive, so I think we are on the right track."
It would be nice to be racing with the Renaults or the McLarens again but I am not sure we will be doing that
Jenson Button, who was 11th overall, said he did not expect his Honda team to repeat the form they showed in Germany last weekend, when he finished fourth.
"This will be a difficult weekend, if we can get some points I will be happy," the Englishman said.
"It would be nice to be racing with the Renaults or the McLarens again but I am not sure we will be doing that.
"It's a circuit we have found tough in the past. But if we go well here I think it shows we have made progress. If we don't we don't.
"You're only just as good as your last race. Hopefully we will have a good race here, that's our aim. We don't want to think let's forget this one and move on. We want to get a good result.
"I'm not getting too excited. We really have to wait and see how this weekend goes before we say we have made a good step forward.
"We have to be a little bit careful, I don't want to be too positive about our steps forward yet."
Combined times from Friday practice for Hungarian Grand Prix:
1. Kimi Raikkonen (Fin) McLaren-Mercedes one minute 21.624 seconds**
2 Felipe Massa (Brz) Ferrari
3. Anthony Davidson* (GB) Honda 1:22.396**
4. Michael Schumacher (Ger) Ferrari 1:22.499**
5. Pedro de la Rosa (Spa) McLaren-Mercedes 1:22.730**
6. Alexander Wurz* (Aut) Williams-Cosworth 1:22.941**
7. Fernando Alonso (Spa) Renault 1:23.097
8. Giancarlo Fisichella (Ita) Renault 1:23.189
9. Robert Doornbos* (Ned) RedBull-Ferrari 1:23.195
10. Rubens Barrichello (Brz) Honda 1:23.553**
11. Jenson Button (GB) Honda 1:23.659**
12. Ralf Schumacher (Ger) Toyota 1:23.747
13. Jarno Trulli (Ita) Toyota 1:23.771
14. Nick Heidfeld (Ger) BMW Sauber 1:23.934
15. Robert Kubica (Pol) BMW Sauber 1:24.106
16. Markus Winkelhock* (Ger) MF1-Toyota 1:24.381
17. Tiago Monteiro (Por) MF1-Toyota 1:24.508
18. Takuma Sato (Jpn) Super Aguri-Honda 1:24.623
19. Nico Rosberg (Ger) Williams-Cosworth 1:24.793
20. Neel Jani* (Swi) Toro Rosso-Cosworth 1:24.854
21. Christijan Albers (Ned) MF1-Toyota 1:25.038
22. Scott Speed (US) Toro Rosso-Cosworth 1:25.152
23. Mark Webber (Aus) Williams-Cosworth 1:25.393
24. Vitantonio Liuzzi (Ita) Toro Rosso-Cosworth 1:25.477**
25. Christian Klien (Aut) Red Bull-Ferrari 1:25.647
26. David Coulthard (GB) Red Bull-Ferrari 1:25.843
27. Sakon Yamamoto (Jpn) Super Aguri-Honda 1:26.877
* = test driver not eligible to race; ** = time set in first session