Renault boss Flavio Briatore believes Heikki Kovalainen's progress is being hindered by an under-performing car.

After a wretched debut in the season-opening Australian Grand Prix - one that was heavily criticised by Briatore - the Finn has since improved to finish eighth in Malaysia and ninth in Bahrain, each time closely behind team-mate Giancarlo Fisichella.

Briatore said: "Melbourne was bad - Heikki admitted so - but since then he has focused, worked hard and improved. For a rookie, though, it's very hard to do the job when you don't have the right car underneath you."

He added: "Look at Lewis Hamilton - he is driving very well, but it is happening because he has confidence in the car (McLaren).

"Even Fernando Alonso, at Renault in 2003, had a car he could really trust.

"Heikki doesn't have that at the moment, and it makes it much harder for him to make a big impression.

"But he has shown he is tough, that he can bounce back from adversity, and that he can be quick.

"He is learning a lot at the moment, and that will really help him in the future."