Juan Pablo Montoya fears Sunday's Italian Grand Prix, Ferrari's home race, could prove the toughest challenge remaining for championship-leading Williams this season.

But the Colombian, who could oust Ferrari's Michael Schumacher from the top of the standings at Monza, was confident that he still had a good chance of winning at the circuit where he celebrated his first victory two years ago.

"I think they should all be pretty good for us," he said of the final three races of the season at Monza, Indianapolis and the Japanese Grand Prix at Suzuka.

"I think the tightest race will probably be this one."

Schumacher leads the championship with 72 points, while Montoya has 71 and McLaren's Kimi Raikkonen 70.

Williams and McLaren will both have to run with a new design of front tyre after Michelin were accused by Ferrari and Bridgestone of using an illegal amount of tread in some circumstances.

Montoya, who has started on pole for the last two years at Monza and last year clocked the fastest qualifying lap in Formula One history, shrugged off the entire controversy.

"We changed tyres and the FIA are happy with it and we are happy with them as well," he said. "I think we did very good long runs last week, we were very competitive on lap times.

"I think last week it was very hard to say how competitive you really are because everyone was running different fuel levels. We will see this weekend how competitive we are.

"I think we are very competitive," he said.

Montoya, who has won the Indy 500 and CART titles, said taking the Formula One crown would be the pinnacle of his career.

"It would be the biggest thing I have won," he said. "It is the biggest thing in motorsport. So it would be nice, but there are no guarantees. I just take it as it comes."