Motor racing-Vettel fears Mercedes have widened the gap

BARCELONA, May 9 (Reuters) - Sebastian Vettel, the only driver so far this season to deny Mercedes a victory, feared on Saturday that the gap between Ferrari and the Formula One world champions had widened.

"The gap is probably a little bit bigger than it was the last couple of races," the four times world champion told reporters after qualifying third at the Spanish Grand Prix, the first race of the season in Europe.

"I don't think that's down to one thing only -- I think there's always a lot of things you throw in the bag and maybe we are struggling a little bit more this weekend," added the German.

Vettel won the second race of the season in Malaysia, when drivers were given the same choice of medium and hard tyres as at the Circuit de Catalunya, but he played down any similarities.

At steamy Sepang, Ferrari got their tyre strategy spot on while Mercedes also made mistakes. at the Circuit de Catalunya on Sunday, Mercedes appeared to have the situation under control.

World champion Lewis Hamilton, team mate Nico Rosberg and Vettel all managed to save a set of medium tyres -- faster than the hard option -- for the race, with two stops expected to be the norm.

"We have the same tyres, it's correct, but it's a completely different circuit (to Malaysia) as well. I think potentially the tyres are not working as well as they used to in Malaysia," said Vettel.

"It looks like Mercedes have a bit of an edge and are more comfortable on both compounds, compared to us. So, we'll see what we can do in the race."

Double world champion Hamilton, who leads Rosberg by 27 points, has won three of the four races so far but Rosberg starts on pole for the first time this year. (Reporting by Alan Baldwin, editing by Justin Palmer)