Wednesday 20 August at 10:17 : F1 teams are still undecided about whether to use KERS systems on their cars next year, according to Toyota's engine boss Luca Marmorini.

Some teams, most prominently BMW-Sauber and Red Bull, have notably struggled in the current development phase of the energy-recovery technology that is set to debut in 2009.

But Marmorini revealed recently that "all teams are having problems" with KERS at present.

He now tells Switzerland's Motorsport Aktuell: "You don't really need the 400 kJ (per lap output).

"You don't have to use KERS," Marmorini added.

"The FIA has given us full freedom of choice. You always have to consider: the car has to be fast."

Another crucial consideration, he explained, is that KERS failures are likely to cause cars to retire from grands prix.

It is understood that Toyota is among the number of teams who believe a gentleman's agreement to delay KERS until 2010 should be put in place -- primarily on the grounds of safety.

"We are very cautious about such matters," Marmorini confirmed. "Toyota has a lot of experience with this type of technology for road cars, and so safety is our main consideration."