Red Bull motorsport advisor Helmut Marko has conceded that it could take half the season before Red Bull is in a position to outpace Mercedes.
"Mercedes is still the favourite," Marko told Sky Sports this week. "They have the fastest engine, they have the best driveability.
"Renault is catching up. How much? We will see when we come to Melbourne but we are positive that we could come very near to them mid-season or so.
Marko added that the Ferrari was also looking strong, and seemed to be showing some good reliability so far in pre-season testing.
"I think it should be a fight between Mercedes, Ferrari and us," Marko said. "How close we are and the rest? We will see during the season."
The new tyre and downforce regulations introduced this season give Red Bull the chance to narrow the gap to Mercedes. Marko said he was in favour of how the 2017 cars were shaping up.
"The car looks much better, more aggressive, more sexy," he said when asked about the RB13.
"What I have seen in the fast corners, the cornering speed is amazing so I'm sure we will see much faster lap times.
"Overtaking I'm not so sure, they are braking so late it will be difficult.
"Let's see when people are running with the same amount of weight and with full horsepower," he concluded. "I think it could be an interesting season."
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