Hamilton kept alive his own chances of another championship during Sunday's Chinese Grand Prix by finishing third, his second podium finish in as many races. After three rounds he stands fourth on 40 points, 12 behind Vettel.
But he said on Monday: "I think Ferrari are the quickest. They showed in China [where Alonso won] they are the quickest overall. The best driver has got the quickest car at the moment, so that is going to be tough to beat. Fernando didn't have the quickest car last year, but he did a solid job by scoring points all the time."
There is very little between the four leading teams: Red Bull (78 points), Ferrari (73), Lotus (60) and Mercedes (52), with McLaren and Force India both on 14, fighting it out for fifth spot at this stage.
Hamilton has not ruled out his own chances of adding to his 2008 title. "I definitely feel like a championship contender at the moment, but I'm not focusing on that because you never know," he said. "Look at Nico [Rosberg's] car, which didn't finish. That could happen to me at any stage.
"But I have a different outlook this season. I came into the year with everyone saying it was the worst decision [leaving McLaren for Mercedes] I could possibly ever make in my life. I didn't know what the car was going to be like, but we are getting these results. We are hanging on by the skin of our teeth, but we are doing the job.
"We have got a lot of work to do to improve reliability and to pick up the pace. But we are on it and doing the best job we can. I think pole flattered us a bit in China. The car is quick over a single lap, but we just need to pick up the race pace."
Hamilton admitted he was hanging on for third place at the end as Vettel closed in on him. "I got some backmarkers which was a bit unfortunate. I thought: 'Just my luck!' I was very happy that I was able to keep it together until the finish line. I thought it was going to be very close, one more lap and he would have had me for sure. Fortunately he didn't."
Looking forward to Sunday's race in Bahrain, he added: "It will be very hot. Fernando will be very quick, and the Red Bulls and the Lotus. To finish as high as we have will be tough, but we'll give it our best shot.
"Bahrain, hopefully, will be a better weekend for us. China is a very front limited circuit and it is all about looking after the front tyres. Next weekend is all about the rear tyres and whether or not we can look after them."
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