"We are certainly lighter than other people-and that is why we are first — but I have a feeling that we are quicker than normal and we are going to drop back less.

"I hope we can do a top five in qualifying, which is great. It is my home, Monaco, so I really enjoy driving here. It is such a challenging track and it is very, very difficult."

The 23-year-old German, son of former champion Finn Keke Rosberg, clocked a best time of one minute and 15.243 seconds.

He was two-tenths of a second quicker than last year's race winner defending world champion Briton Lewis Hamilton who was second fastest in his McLaren Mercedes.

Hamilton optimistic

Veteran Brazilian Rubens Barrichello, who had been quickest in the morning's opening free practice session, was third fastest for the Brawn GP team ahead of his team-mate championship leading Briton Jenson Button.

Brazilian Felipe Massa was fifth for Ferrari ahead of much-fancied German Sebastian Vettel of Red Bull, Finns Heikki Kovalainen of McLaren and Kimi Raikkonen of Ferrari.

Hamilton said he felt optimistic. He said: "From today's results, I definitely feel Q3 should be possible this weekend. Here the most important thing is to be as close to the front as possible, if not on the front row. But to beat the Brawns will be tough."

Hamilton said he was relishing driving around the streets of Monaco. "Driving Monaco is a spectacular thing," he said. "You can never compare it to any other circuit you go to, or any other experience. It really is such a huge buzz, it feels amazing."