Rubens Barrichello says Ferrari team mate Michael Schumacher can expect a fight for the Formula One crown, despite the German's eighth win in nine races at Sunday's U.S. Grand Prix.

Brazilian Barrichello challenged the six times world champion more than ever at Indianapolis, racing side by side and even putting a wheel on the grass as he tried to overtake.

"Our drivers were free to race one another and we just told them to be sensible and not have an accident," said Ferrari technical director Ross Brawn.

If the outcome remained the same, with the disappointed Brazilian anchoring Ferrari's sixth one-two of the season after starting on pole and setting the fastest lap, Barrichello kept his hopes up.

"I am now keener than ever to win a race as soon as possible," he said.

With half the season completed, Barrichello is just 18 points adrift of Schumacher and is the only driver to have finished every race in the points.

A retirement for Schumacher and a win for his team mate in the next race would put the Brazilian back within striking distance, assuming Ferrari allow him to mount a genuine challenge.

With the points system rewarding reliability, Schumacher could conceivably win 13 races and still lose the title to Barrichello if the German has five retirements and his team mate finishes second to the end of the season.

It would take a miracle, but Barrichello could still dream.

GO FAST

"If you see that I have 62 points in the championship and last year, in the whole championship, I had 65 then I still have a chance this year," said Barrichello.

Two years ago Ferrari caused uproar at Indianapolis when, after a "team orders" furore in Austria, Schumacher slowed at the finish and Barrichello took the chequered flag.

Blatant manipulation of a race is now outlawed and Ferrari, utterly dominant and with a 76 point lead in the constructors' standings, emphasised that their drivers had been unleashed.

"They know that they don't want to see each other out of the race but they are going to push as hard as they can without overstepping the mark," said Brawn.

"So it's really up to their judgement, what that limit is. They may make a mistake.

"I think our motto is 'go fast and don't crash' and that's all we ask them to do. But there will be occasions when they'll trip over each other.

"We've been fortunate that it hasn't happened."