Valtteri Bottas led a Mercedes one-two in the last race in Azerbaijan with Sebastian Vettel third

Sebastian Vettel has stressed that his Ferrari team need to start beating Mercedes after the world champions' dominant start to the season.

Mercedes have taken one-twos in all four races and Vettel is 35 points off championship leader Valtteri Bottas, who is one ahead of Lewis Hamilton.

Vettel said: "We need to start scoring points, the sooner the better. The longer it goes on, the worse it looks."

But he said his chances of the drivers' title were "as good as anybody else's".

The German is in agreement with Bottas that Mercedes' results have made them look more superior than they actually are, in terms of the competitive standing between the two cars.

Vettel said: "[Overall], we are slightly behind but we know it is not a long way and things could go our way. Everyone is fired up and willing to fight."

Finland's Bottas added: "If you look at the results, it looks like we had been dominating as a team but by pace there is not that much difference between us and Ferrari. It is depending on the weekend.

"Melbourne we were better, Bahrain they were, after that it has been pretty close and down to fine details."

Bottas has won two of the opening four races of the season with his Mercedes team-mate Lewis Hamilton winning the other two

Both teams have performance upgrades for this weekend's Spanish Grand Prix.

Ferrari have introduced a more powerful engine, including a new fuel, as well as aerodynamic improvements, while Mercedes have their own aerodynamic upgrades.

Bottas said: "This weekend with the upgrades Ferrari is bringing, they have a new power unit, we see how it works. We have some upgrades, [you] can't rule out Red Bull at this kind of track, same as Monaco, but it is going to be a lot about development and how we can improve through the year."

Vettel has admitted that Ferrari have been struggling to get their car back into the sweet-spot of handling balance that they achieved at the Circuit de Barcelona-Catalunya in testing in February and March.

The four-time world champion said it would be "interesting" now they were returning to the track for a race whether they could find it again.

"The car was really good in testing," Vettel said. "But we arrived in Australia and struggled to feel the same.

"The last four races have been up and down, there have been times when it felt good and times when it did not.

"Deep down, we know the car is strong but we haven't found the silver bullet. There never is one. It is getting into the details and trying to understand more and more and trying to improve and make sure it doesn't happen again.

"This weekend will be interesting for us because we had such a good feeling and it was not so long ago. I remember how the car felt. if we can get back to that feeling I am confident we can be very competitive."

'Respect is there' amid the tension at Mercedes

After the last race in Baku, Hamilton rued his decision to give Bottas more space than he would have given another driver when he was alongside at the first corner.

Asked whether he would show more aggression towards his team-mate with the championship fight so close between them, the Briton said: "It will always be respectful. We'll see. Ultimately, the core goal is for the team to finish at the top, and I am a team player.

"We are not going to be touching but in terms of giving up positions, that won't be happening again."

Hamilton hinted that there had been tension in the background already, but that it was under control.

Asked why he thought the fight would not deteriorate into extreme tension between the drivers as it did with his former team-mate Nico Rosberg who won the title in 2016, Hamilton added: "There are things that happen in the background that you won't know about. I don't feel this is the place to talk about it.

"When [Mercedes team boss Toto Wolff] mentions glimpses of that, he has seen a glimpse of it but what is really important is we have discussed it and rectified it and it won't spring up again, whereas what happened before was an individual continued to go down that route.

"But that's not what we have here. We have a really great energy in the team.

"The respect is there. We have agreed rules set out so we do finish the races one-two and we play supporting roles either way, and I truly believe it is the best pairing in terms of that respect in terms of how we deliver each weekend that any team has ever had or currently has.

"Yes, it's going to be close and there is always tension when you want to beat someone else but the fundamental key is we are team players, we are not here for ourselves. Of course we want to win the championship individually, but we are paid to win and deliver for the team."