Motor racing-Hamilton retirement caps poor Mercedes weekend

* Hamilton encounters power problems * Briton retires at the end of lap 32 (Adds Rosberg quotes) By Patrick Johnston SINGAPORE, Sept 20 (Reuters) - Formula One world championship leader Lewis Hamilton retired from the Singapore Grand Prix on Sunday after encountering power problems in his Mercedes to cap a disappointing weekend for the dominant team. The British driver, who had not suffered a retirement since Belgium last year, drove into the pits at the end of lap 32 after his team failed to resolve the issue over six laps. "I was feeling super optimistic and easily keeping up. I was hoping for a quick fix but it never came," the Briton, who was chasing a 41st career win to equal the mark of his late idol Ayrton Senna, told the BBC. Hamilton, the reigning world drivers' champion, was riding in fourth having picked up a place from his third-row starting position when he complained over his team radio about issues with his car. "Lost power guys, lost power," the 30-year-old said on lap 26 before tumbling down the field as his team tried in vain to figure out the cause of the problem. The double world champion fell to the back of the pack over the next laps before his team eventually called him in after the driver asked to be stopped. "They (the team) were telling me to change all these things and then I was overtaken by two Manors so I knew I was last," he told Sky Sports. "When they started to pull away, I knew it was over." Hamilton has enjoyed mixed fortunes under the floodlights of the Marina Bay Street Circuit, winning in 2009 and last year but also being forced to retire while leading in 2012 with former team McLaren. Ferrari's Sebastian Vettel took the chequered flag for his 42nd career win, with Nico Rosberg fourth for Mercedes which allowed him to cut the gap on Hamilton to 41 points in the title race with six races remaining. Vettel's victory left the quadruple world champion 49 points behind Hamilton. Rosberg, though, was unhappy with how the weekend had gone in Singapore where he struggled for pace behind the Red Bulls and Ferrari as Mercedes finished off the podium for only the second time this year. "Of course there is the small positive of closing the gap, but the big one is that it has been such a disappointing weekend for all of us," he told SkySports. "To be so far off the pace and not understand it - that is really bad, because then how are you going to improve it? "You just hope that at the next track it's going to come towards us again. The chances are extremely good because at all other tracks we've been so fast, but who knows? As a team it's been very disappointing." Rosberg was unsure whether Mercedes could recover for next weekend's Japan Grand Prix. "Today is very worrying, particularly because we don't know why it is like that. So who knows if it will be like that at the next race or not." (Editing by Martyn Herman)