Formula 1 world champion Lewis Hamilton admits he and his Mercedes team were not expecting Ferrari to hold the advantage they did in qualifying for the Chinese GP.

Championship leader Sebastian Vettel made it two consecutive pole positions with a brilliant lap to beat teammate Kimi Raikkonen by a narrow margin in Shanghai on Saturday, while the Brackley-based team were unable to compete.

For the second straight weekend, the Briton was also beaten by his partner Valtteri Bottas with the Finn claiming third by half a tenth of a second.

But it was the deficit to the Scuderia which most concerned Hamilton with his time almost six-tenths down on the new lap record set by Vettel.

"The car felt OK but I don't really have the answer for it," the 33-year-old said to reporters later.

Mercedes motorsport boss Toto Wolff was also taken aback by Ferrari's pace but does think he has an explanation for his team's lack of pace.

"It's tricky. We are lacking grip," the Austrian explained. "You can fall out of the window by the tyres getting too hot or being too cold. It's two extremes like we had in Bahrain. I think it's a tyre issue."

With conditions for race day expected to improve from the cool, cloudy weather of the first two days, Hamilton is hopeful that could result in a change of luck.

"It's a lot hotter tomorrow so it will be a challenge to see if we can keep up with them," he admitted.

"I think it's in the top three of the easier tracks to overtake, [but] the Ferraris are too fast on the straight so it will be interesting.

"I don't know if we can challenge – we were half a second behind today," Lewis added.

"We were quicker in the last race but they were able to hold on and will probably do the same tomorrow."

Both Ferrari and Mercedes have chosen the same approach on strategy as they will start on the slower but more durable Soft compound compared to Red Bull behind on the faster but high-degrading Ultrasoft.

Just how the change in the weather will impact the relative performance of the two tyres will also be crucial in deciding if a three-team battle is on the cards in China.