Raikkonen won't use KERS at Sakhir

Ferrari opted out of KERS completely in China after previous reliability problems, but Massa in particular felt that the loss of the device had made the car even less competitive.

AUTOSPORT understands that Raikkonen's weight makes the KERS decision particularly marginal on his car. Ferrari is set to introduce a new lighter-weight chassis for him in the next race in a bid to improve this situation, with the chassis undergoing crash testing yesterday.

But despite this, Raikkonen says he will not return to KERS yet.

"I won't use it tomorrow," said Raikkonen. "The other car will run it tomorrow and then we will make a decision about which way we go. We want to look a little bit to compare the two cars and see what difference it makes."

McLaren has suggested that the long straight and heavy braking areas at Sakhir will make KERS more useful than at any other race this season, but Raikkonen is still unsure how much benefit the device offers.

"It is probably faster in quite a few places, but the car was not too bad in the last race after qualifying," he said. "We could have been faster with it there, but there is not much difference driving with or without for us."

Of the other teams using KERS, BMW's Nick Heidfeld is set to continue with the system in Bahrain, while Renault - which also opted against it at Shanghai - is likely to run KERS in Friday practice before deciding its plans for the rest of the weekend.