Fernando Alonso has revealed that Ferrari's new car still needs to be considerably improved before the beginning of the Formula One season.

The Spaniard set the fastest time on the fourth day of testing in Jerez but believes that the F2012 can still be modified.

Alonso told Sky Sports News: "We learned a lot about the difference of the car [compared to last year's], it's been a learning test for us, a lot of constant speeds for us to do the aero and mechanical tests.

"Overall, it has been a positive four days for us and understanding the car. But obviously with a completely new concept and a completely new design there is a lot of room for improvement for us and that's what we need to focus on in the next couple of tests."

Alonso has won the World Championship on two occasions.