Jenson Button believes he can challenge for the World Championship but not until 2003 at the earliest.

The 20-year-old Brit reckons he will not be in a position to battle for the drivers' crown until he is back behind the wheel of a BMW-powered Williams.

Button competed for the Grove-based team for the final time in last weekend's season-ending race in Malaysia before embarking on a two-year loan deal with the Benetton team at Enstone.

He said: "In 2003, when I come back to Williams, I think I will have a fantastic opportunity to get good results and hopefully be fighting for the championship.

"I have little doubt in the team's ability to be a front runner and I am looking forward to being an integral part of that success over the long term. It would be nice to battle for it next year, but I know that is not going to happen. But I think it is impossible to put a time limit on it. You have got to have the best car and best engine to win the World Championship.

"If just one little detail is not there, you are not going to win it. It could take three years, it could take seven or eight or it might never happen. But if I am with a crack team then hopefully it is not going to take too long."

Button, who failed to finish on Sunday, will be replaced by Colombia's CART champion Juan Pablo Montoya next year.

Button's Williams teammate, Ralf Schumacher, was also sidelined by a malfunction in the engine oil supply system, though the team celebrated third place in the constructors' championship.

Sir Frank Williams said: "This was a disappointing end of the season, but perhaps a gentle prod in the direction of all the things we know we have to put right for next year."

Benetton held on to fourth place in the constructors' championship and Giancarlo Fisichella finished sixth in the driver's championship.

The Leafield-based Orange Arrows team had a mixed day. Jos Verstappen came home in tenth place. Pedro de la Rosa went out on the first lap, when his A21 car was hit and damaged in an accident at the second corner.

The race summed up the ill fortune suffered by the Benson and Hedges Jordan team this season as both drivers made good starts but were then hit by problems.