Lewis Hamilton has admitted that he found Ferrari's pace in practice for this weekend's Malaysian Grand Prix "surprising".
Kimi Raikkonen finished just behind the defending world champion for the Italian constructor during the second session at Sepang, splitting the Mercedes cars at the top of the timesheets.
The Briton told BBC Sport: "The Ferraris look great. It's surprising to see how good their times are. We'll see whether that continues through the weekend.
"My lap wasn't spectacular. There are some improvements I can make with the balance and the settings but they were just all brought from the last race. I'm sure we will improve it a little bit.
"I got a fairly decent lap but we haven't dialled the car in, changed the differential settings or changed the set-up at all. So there is definitely some work to do."
Hamilton was fastest in P2 after failing to set a time in the first session with an engine problem.
