Ferrari have admitted they fear their world title hopes could be hit by a performance deficit in their tyres.
Ferrari technical boss Ross Brawn said the team were waiting on improvements planned by tyre partner Bridgestone.
"Bridgestone have strengthened their operation considerably, but the benefits may take a while to come through," he said.
It is widely thought that Bridgestone's tyres are not as fast as the Michelins used by McLaren and Williams.
Brawn added: "We will succeed or fail on the strength of our tyres.
"This doesn't mean we expect Bridgestone to shoulder the burden alone. We are not saying: 'It's up to you, Bridgestone.'"
"We'll succeed together and we'll fail together."
Reigning champion Michael Schumacher was more positive about Bridgestone's progress over the winter.
"There's been a lot of discussion about tyres. If I'm
correct, last year I think we won both championships with those
tyres. So it can't be that bad," he said.
"We have been looking very strong at the last test in
Barcelona, so all in all I think we are ready for the game."
Schumacher said he saw McLaren's Kimi Raikkonen as his main threat as he goes for an unprecedented seventh title - ahead of Williams drivers Juan Pablo Montoya and Ralf Schumacher, his brother.
"Williams and Renault have brand new cars," Michael Schumacher said, "but McLaren have a car they already know very well."
He added that he thought Raikkonen would do a "very good job again" this year.