Formula One leaders Mercedes singled out Ferrari as their main championship challengers on Thursday but Fernando Alonso was quick to play down his chances of a top three finish at his home Spanish Grand Prix.

Alonso has not won since he triumphed in front of his home fans at the Circuit de Catalunya last year and Mercedes duo Lewis Hamilton and Nico Rosberg remain the overwhelming favourites for Sunday's race.

Mercedes have won all four races so far but Alonso's third place in China last month indicated Ferrari had taken a step in the right direction - an improvement recognised by Mercedes motorsport head Toto Wolff.

"I think it will be Ferrari," the Austrian said when asked who would be his team's main title rivals. "They are the only other team to have everything, car and powertrain, in-house. And I reckon Alonso to be a real race monster who can achieve everything."
Alonso recognised the compliment but refused to go along with it.

"If they count on us for the championship fight it's good news because they respect us," he told a news conference. "But we need to deliver if we want to become really a threat. We are working on that. We are not in a position that we are happy with," he said. "We start with some deficit to the top teams and especially Mercedes."

Ferrari are fourth overall in the constructors' standings, with 52 points to Mercedes 154. Champions Red Bull are second on 57 and Mercedes-powered Force India third on 54.

Asked whether another podium was within his reach this weekend, Alonso shook his head.
"I don't think so. We cannot start the weekend thinking to be on the podium or thinking to win the race. That will be creating false targets to everyone," he said.

"We know it's going to be a tough weekend and it's not going to be easy. Anything can happen but today sitting here if I tell you I will fight for the podium, probably I will lie to you and I don't want to do so for all the people coming."

Ferrari have an upgrade to their car and the characteristics of the Spanish circuit will also help them but the Spaniard expected Mercedes to remain ahead of the rest.

Sitting next to Red Bull's quadruple world champion Sebastian Vettel in the news conference, the Spaniard smiled when he and the German were asked how long they could bear not winning.

Vettel won the last nine races of 2013 but has not come close to winning this year with his Renault power unit still behind on performance compared to Mercedes.

"Unfortunately, I have a lot more experience (of waiting for a win)," said Alonso. "You just try to do the best job you can and try to find different goals. My last win was here last year so it's one year without victories and I would like not to have that long period.

"On the other hand, we are 22 drivers on the grid and maybe 20 are in a worse position than me. I am an extremely lucky and very privileged guy."