Niki Lauda insists there is all to race for despite Lewis Hamilton dominating opening rounds ahead of Spanish Grand Prix

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Niki Lauda insists there is still all to race for in the 2015 Formula One championship despite Lewis Hamilton's impressive start to his title defence.

The Briton has taken three victories out of the opening four rounds as he looks to win a third drivers' championship, taking a second-place when the Ferrari of Sebastian Vettel proved too strong for the usually-dominant Mercedes in Malaysia.

And Lauda, himself a three-time world champion and now a non-executive chairman at Mercedes, believes that showing proves Ferrari can push Hamilton and team-mate Nico Rosberg all the way - starting at this weekend's Spanish Grand Prix.

Lewis Hamilton celebrates wining the Bahrain Grand Prix, his third victory from four races

Mercedes chief Niki Lauda insists there is still all to play for this season

Hamilton heads to Barcelona's Circuit de Catalunya hoping to extend his lead at the Spanish Grand Prix

'The season is not finished, it (the Spanish Grand Prix) is the fourth race only,' he said.

'Ferrari is very strong, there is no question about it, and as a racing team you should never think that nobody can catch you, then you make a big mistake.

'Ferrari has closed the gap from last year to this year to zero. I think they increased their engine by about 45 horsepower, so my estimate at the moment is that they have the same engine power as the Mercedes has and now it depends on the car and what the drivers can do - and there will be close racing all the way through the season.

'The best of the rest at the moment is Ferrari, there is no question, and then Williams for me is a little bit disappointing at the moment, but I know that they will bring some upgrades, so then they should be okay.'

Sebastian Vettel managed to break Mercedes early season dominance with victory in Malaysia

Hamilton heads into the race at Barcelona's Circuit de Catalunya in good spirits following another impressive victory in Bahrain - but is expecting to be pushed in Spain.

'Bahrain was a tough race so to come away with the win was a great feeling and it's amazing the start we've had this year,' he said.

'Next up it's Barcelona, which is a great place to start the European phase of the season. The weather is always good and the circuit is a real test of every aspect of the car, which is why we go testing there.

'Racing there is tough - it's usually hot and the circuit is incredibly physical but the support I have in Spain is growing every time we go and, having tasted success there for the first time last year, I want to do it in even better style this time.'

Hamilton's strongest challenge is likely to be presented by team-mate Rosberg who showed in Bahrain that he is willing to mix it on track to get his title tilt into motion.

Hamilton's Merecdes team-mate Nico Rosberg (left) is expected to be his closest rival

The German has not won in 2015 and has been out-performed by Hamilton on a regular basis but, although he had to settle for third in Bahrain after his brakes let him down towards the end of the race, Rosberg is invigorated to start showing why he pushed his team-mate so close last season.

'The race in Bahrain was definitely the most enjoyable of the season for me so far,' he said.

'It was a really good fight out there and it gave me the chance to show what I can do in a close battle. Although we had a problem at the end, the car felt fantastic and I could really push hard to get my positions back.

'I'm feeling really fired up for the next races knowing I have all the tools available to me for a strong performance. It's felt like a long break and I can't wait to get back out there in Barcelona.

'It will be interesting to see how each team has developed since we last came here in the winter and also to see who has brought the most upgrades since the last race.'

McLaren, driven by Fernando Alonso and Jenson Button, will debut a new look car in Spain

Hamilton's former team McLaren have revealed a change to the colour scheme of their cars ahead of the weekend.

The Woking-based team have endured a torrid start to the 2015 and remain without a world championship point as Jenson Button and Fernando Alonso struggle to make the most of a car down on power compared to the rest of the field.

But the team are hopeful of making a step forward in Barcelona with improvements coming from both chassis and the Honda power unit and now the team has unveiled a new look, with a grey and orange livery replacing the silver which has been a mark of McLaren since 1997.

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