Lewis Hamilton believes it will be difficult to halt Ferrari's winning start to the season at the Chinese Grand Prix but still thinks Mercedes are the strongest team.
Sebastian Vettel followed up his victory in the season-opening race in Australia by topping the podium in Bahrain last Sunday.
Mercedes have claimed four successive wins at the Shanghai International Circuit, but reigning world champion Hamilton is braced for a battle with the Scuderia this weekend.
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The Brit said: "They are going to be hard to beat. Their straight-line speed in the last few races has been faster than ours and we have the longest straights here. So I'm anticipating they will be very, very fast and hard to beat.
"They are faster than us on the straights and as quick as us through the corners. Their engine programme has really taken a big step this season. It will be interesting to see how their reliability will be - as it will be for Renault and us.
"This should be a good track for us but I think it's going to be close."
Hamilton expects it to be more difficult to fend off the Ferrari challenge this season but the four-time world champion is content that Mercedes are well equipped for more glory.
"I still believe we are the best team. We definitely have the potential to win races and to fight for this championship. But what's important is that we all stay on our toes." he added.
"We all need to be performing at our utmost and it's even more crucial this year as it's magnified because we are so close.
"Ferrari are really performing well - and both Kimi [Raikkonen] and Sebastian are performing really well - so l think it's a tougher season than last year. Ferrari have got a very fast car and there are millimetres between us."