Kimi Raikkonen says an unknown problem with the left rear of his Ferrari hampered his running during Friday practice for the Hungarian Grand Prix.

Having been third fastest in FP1, Raikkonen slipped to sixth in FP2 as Ferrari enjoyed an encouraging day in terms of one-lap pace. However, Raikkonen said his afternoon session was compromised by a problem which did not appear on the team's telemetry and is hoping an explanation can be found before FP3.

"In the first free practice session, we managed to do a good job, testing various solutions on the programme and I was feeling reasonably pleased with the handling of the car," Raikkonen said. "Then, in the afternoon, I went out for a second run on the Medium tyres, because the behaviour of this compound seemed worse as the temperature went up and that affected the handling of the car, while on the Soft I had no problems.

"In the second part of the session I did a race simulation with both compounds: unfortunately when I fitted the Mediums I had a problem with the left rear and I had to pit earlier than planned. The telemetry didn't show any problem on the car, so I hope that the data will point us in the right direction for the next two days."

Despite Friday's times, engineering director Pat Fry believes Ferrari is set to struggle if it can't pull out a good result in qualifying.

"The performance level over short and long runs are similar to those seen in recent races and it looks like being a very tough weekend," Fry said. "Overtaking opportunities are strictly limited and so, more than elsewhere, you need to get the best possible result in qualifying."