Lewis Hamilton says he is concerned about the "threat" posed by Ferrari in Sunday's Chinese Grand Prix despite taking his third consecutive pole.
Hamilton edged out Mercedes team-mate Nico Rosberg to join Ayrton Senna, Michael Schumacher and Juan Manuel Fangio as the only drivers to score five or more poles at one track.
Hamilton is wary of Ferrari, despite qualifying 0.905 seconds quicker than Sebastian Vettel, who won in Malaysia.
"It's not over by any means," he said.
"The Ferraris are very good. They are not that far behind pace-wise so they could still be a threat with their long-run pace.
I have to make sure I do lots of work to make sure I finish where I want to.
"There is a long, long race ahead of us, so I am just trying to keep myself calm.
"They are maybe able to go a lap longer and Nico is going to be very quick in the race as well."
However, he admitted he felt he did have the speed to win the race - held in the cavernous and often smog-filled Shanghai International Circuit, which begins at 07:00 BST on Sunday.
"I think we do potentially have pace on them on the long runs," Hamilton said.
Hamilton's pole was his fifth in China.
The Briton has looked imperious in Shanghai so far this weekend, topping all practice sessions other than the first part of qualifying, when the only reason Ferrari beat him was because Mercedes did not use the faster 'soft' tyre and the Italian team did.
|Ferrari v Mercedes - perfectly matched? Andrew Benson's analysis|
|"Ferrari won in Malaysia thanks largely to their ability to preserve their tyres better than Mercedes, allied to a pace good enough to enable them to translate that into a race-long challenge. And there were hints on Friday that this may become a running theme this season.|
|While Lewis Hamilton was on average 0.7secs a lap quicker than Kimi Raikkonen on their soft-tyre race simulation runs, the Ferrari hung on to its tyres better.|
|Hamilton was showing significant drop-off after 11 laps; Raikkonen was still going strong after 14. How this will play out on Sunday is a fascinating question."|
But Vettel's victory in Malaysia, which was founded on their more gentle usage of tyres and doing one fewer pit stop, has created a sense of concern and alert at Mercedes, despite their obvious pace advantage.
Mercedes F1 boss Toto Wolff said Ferrari were "a real threat", adding that they needed "to be careful" in the race.
The team's technical boss Paddy Lowe added: "Our competitors have strong pace and we will have our work cut out."
Lowe added that the decision not to use the 'soft' tyres in the first part of qualifying was based on keeping unused tyres for the race, which is a small but potentially important advantage.