Formula One world champion Lewis Hamilton cast doubt on his Chinese Grand Prix chances after Sebastian Vettel led a Ferrari front row lockout in qualifying on Saturday.
"I don't know if we can challenge, we're half a second behind today," the Mercedes-GP driver told Sky Sports after aborting his final flying lap and taking fourth place on the grid with teammate Valtteri Bottas third.
"Honestly I can't tell you if we can challenge. We were quicker in the race in the last race (Bahrain) but they (Ferrari) were able to hold on. They will probably do the same tomorrow."
Vettel, like Hamilton a four-time world champion, has won the first two races of the season and built up a 17-point lead over the Mercedes driver.
The German was 0.530 seconds faster than Bottas in qualifying and 0.568 quicker than Hamilton, who has won an unprecedented five times previously in Shanghai and arrived as a favourite.
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Mercedes team boss Toto Wolff said making the tyres work was the problem.
"They (Ferrari) have been really strong already in the morning, but qualifying performance they put one on top and we have something to think about," the Austrian said.
"We're lacking grip. You can fall out of the window by the tyres getting too hot or being too cold. They are two extremes like we had in Bahrain and I think this is what happened. I think it's a tyre issue."
Sunday is expected to be a lot warmer than Saturday's windy and cold conditions and Wolff hoped Mercedes had got their race set-up right and could show better pace than their rivals and make the most of strategy.
Hamilton, who will start on the soft tyres as will Ferrari, sounded less sure.
"I think it (the track) is in the top three of the easier ones to overtake ... but the Ferraris are too fast on the straight so it will be interesting," he said.
Bottas said it felt like he had got everything out of the car but pole had still been out of reach.
"Maybe we didn't get the tyres absolutely perfect for the lap but I don't think it would have been enough for us to beat the Ferraris," he said. "That's particularly disappointing because the gap to them is quite big."
"On paper, this track is easier for overtaking than Bahrain, so hopefully tomorrow we can make up for what we lost today."