Alonso: Ferrari favourites for Canada, USA

Although the Renault driver has won the last three races to extend his lead in the championship to 23 points over Michael Schumacher, he reckons Ferrari's top speed will make them very strong in Montreal and Indianapolis.

Renault have vowed to take a more aggressive approach than last year, going for race wins instead of trying to maintain their gap, but Alonso believes they will have to play a defensive game in the North American races.

"For sure if we arrive with 30 points or more than that with the last seven races then it is getting quite good for us but I think it will be difficult to increase," Alonso told reporters in Montreal.

"We are coming to two races where Ferrari are the favourites for the straight-line speed they have and I think we have to defend here a little bit and hopefully finish in front of them. But I think it will be extremely difficult."

The Spaniard, however, is confident Renault will be competitive this weekend.

"We have also a lot of new parts coming for this race, some of them are specific for these two races with low downforce, but some other parts are for the whole year," he added.

"Aerodynamics and new engine coming for Magny-Cours, we need to wait a little bit for Magny-Cours, but a fresh engine for this race we should be very competitive in this race."