By John O'Brien

SINGAPORE (Reuters) - Sebastian Vettel is running out of races to record his first win of the season for Ferrari but the German is optimistic this week's Singapore Grand Prix could provide some belated success for the Italian team.

The four-times world champion joined Ferrari from Red Bull at the start of last term and made an immediate impact, claiming three victories with the last one coming a year ago in Singapore.

This season has been far less fruitful for Ferrari, without a win in 14 races and behind Mercedes and Red Bull in the constructors' standings.

Vettel, though, preferred to look ahead rather than in the rearview mirror when asked about his chances this week.

"All the races that have passed this year we didn't record a victory but looking forward we are always aiming to win," the four-times Singapore winner told reporters on Thursday.

"This track was very good for us last year and we have improved the car from then so we should have a reasonable chance.

"You have to make Mercedes favorites but they had a difficult time here last season. There's no guarantee that it happens again but if they do struggle, then everyone will be happy to take advantage," said Vettel.

Ferrari were expected to mount a serious challenge to Mercedes this term but the German team have won 13 of 14 races and few would have expected Vettel's triumph a year ago to be the last time he climbed on the top step of the podium.

"I don't wake up worrying over how long it has been since my last win," said Vettel who has three second-place finishes and as many third places in 2016.

"Since last year some people have left and a lot of others have been shuffled around. When we started off last year it was clear where we wanted to go, bring Ferrari back to the top.

"It's true we have not had a great season so far but I don't think it has been as bad as some people would lead you to believe. We are critical of ourselves because we have not achieved what we set out to achieve.

"We were closing the gap last year but unfortunately that gap to the top is still there, sometimes bigger, sometimes smaller but still there. We simply haven't been quick enough but we are always working on it," said Vettel.

(Editing by Tony Jimenez)