Sebastian Vettel says "potentially" Ferrari could be a bit closer to Mercedes this weekend in the Chinese Grand Prix, but also warns that it is only Friday and not to put too much importance on the times.

The Scuderia finished the opening day 1-2, with Kimi Raikkonen quickest, 0.109s up on Vettel, while Nico Rosberg was third for Mercedes, 0.128s further back.

"Well, it depends on what the others are doing," Vettel replied when asked if he could get pole position on Saturday. "If we get everything right then potentially we could be a bit closer, but then again it is only Friday today. I wouldn't put too much importance on the times today."

"We had a decent day, the car feels okay and I did one [quick] lap, but for the long run I didn't have the opportunity to see what the other people were doing," he continued.

"Overall I think we can still improve, but the balance is not yet where I want it to be, so let's see what we can do."

Asked if they will need to make progress overnight, Vettel added: "I think we have to. Friday is not that important in terms of position, it is more in terms of feel. The feel is okay but okay is not good, so we can still improve the balance of the car and work tonight to try to get on top of it.

"China is quite brutal on the tyres for everyone and everyone is sliding a lot and tyre degradation is quite high. One lap is good for quali, but in the race you need a lot of good laps in a row."

Meanwhile, Vettel added that the gap to Raikkonen is not of concern: "It is normal to compare, I was looking at some of his stuff but also some other stuff and I think I saw where he was faster. It's easy to see when you can read the lines, but not so easy to do. I think he had a better lap, but we both had a different programme this afternoon."