Button: Ferrari strongest at present

Mark Webber set the best time of the day for Red Bull, with Fernando Alonso second quickest for Ferrari and Button's McLaren third. Alonso and Button both completed several long runs today and Button was impressed by the consistent pace of the Ferrari.

"I think the Ferrari is a very strong car," he said. "If you look at their runs today, they're very consistent. I think they have better consistency than anyone at the moment.

"It's always interesting to observe what they're up to. I think our pace is good, but there are still areas we need to work on for me to be happy with the car."

Button spent some time behind both Alonso and the Mercedes of Michael Schumacher on track today and reckons the Ferrari is handling best so far.

"I followed a few drivers today, Fernando, Michael. It's always interesting to see what's happening," said Button. "You never know what fuel loads people are on but you can see what sort of balance they have.

"The Mercedes to me seemed like it was a little bit twitchy at the rear, and braking it looked like it was locking the rears, but if they're on 150kg it's understandable. It's interesting. The Ferrari looked good on the circuit, good consistency."

And on the performance of the MP4-25, he says McLaren is heading in the right direction but the car is not yet where he wants it.

"For me, our car over one lap is getting there," Button added. "We're improving step by step. And on the long runs, we're improving every run we do. There's so much information we've got from today - more than any other test day, for me anyway. We'll go through all of that this evening and hopefully have another good day of testing tomorrow."