Fernando Alonso on Thursday warned that Ferrari face a difficult month ahead and are likely to struggle at both this weekend's Belgian Grand Prix and next month on home soil in Italy.

The Spanish two-time world champion said it was 'unrealistic' for Ferrari to believe they can win races on pace this season and said the team's main goal was to beat Williams to third place in the constructors' championship.

"Honestly, I think our target has to be lower than many people think," he said. "It has to be fighting for the constructors' championship in the highest position possible. But it is quite a big competition, a tough competition, with Williams.

"The next two races are quite good for them, so we expect to have tough weekends at the moment against Williams here and in Monza, and we need to cope with that.

"We need damage limitation in the next two races in terms of points, and then attack in the last part (of the season). I think a grand prix win this year is a little bit unrealistic."

Alonso acknowledged that both Spa-Francorchamps and Monza — which will stage the Italian Grand Prix on September 7 — will play perfectly to the strengths of the Mercedes-powered teams, including Williams.

And, he said, the next few weeks will not be easy, with Ferrari only seven points ahead of Williams in the fight for third place in the constructors' championship.

Finnish team-mate Kimi Raikkonen, who has a strong record at Spa, said: "It doesn't help really what happened in the past. Obviously, it has been a pretty difficult season so far, but the last race it felt a bit more normal."