Ferrari may have outpaced rivals Red Bull during free practice ahead of the Japanese Grand Prix but Kimi Raikkonen remained frustrated by his car's performance.

As Nico Rosberg and Lewis Hamilton continue to dominate in the Mercedes, the battle behind them gathers pace with the two constructors in the closing races of the season.

The Silver Arrows pair held the top two positions in FP1 and FP2 on Friday, with a Ferrari – Sebastian Vettel and then Raikkonen - claiming third in each of the sessions.

Raikkonen's effort in FP2 left him only three tenths adrift of Rosberg at the top of the time charts in second practice.

That was not enough for the 2007 world champion, though, as he looks to close the gap on third-placed Daniel Ricciardo in the drivers' standings this weekend.

"The balance is not probably where I want it to be," said the Finn.

"My lap time was pretty OK, but feeling-wise I suffered a lot with the understeer and fighting the car through first part of the circuit. It just doesn't feel nice. I was surprised a bit by the lap time.

"It got better in the end, but it's not where we want to be.

"Today the feeling was not very easy, but the lap time was OK. If we can get a good feeling and the car working as we want, we can improve a lot, so we'll see what happens."