And Schumacher believes McLaren's switch to Michelin tyres could prove to be costly.

Schumacher said: "Obviously there is a little question mark concerning McLaren due to them changing tyre company - we don't know how quickly they can adapt to that.

"But Williams and McLaren are the two big threats as usual, except that Williams is in a much better position, for me, this year than they have ever been.

"Although they have put their own chances on a lower level, so as not to build up the pressure too much, I think they are going to be very strong and we are going to face a lot of difficulties from them."

And Schumacher also claimed Scotland's David Coulthard would also be a threat - but only if he can cope with the added responsibility of being the team's most experienced driver following Kimi Raikkonen's arrival as replacement for Mika Hakkinen.

Schumacher said: "I don't know if he can or can or cannot (cope with the pressure).

"David remains David - he is a strong racing driver and he is going to be a challenge to me, no doubt.

"How much is going to be David, how much is going to be Raikkonen, is going to be an interesting question to be answered."