Formula One championship leader Lewis Hamilton promised to come out fighting at this weekend's Japanese Grand Prix after a freak technical mishap in Singapore opened the door for his rivals.

The Mercedes driver failed to finish a race for the first time in more than a year after a simple metal clamp came loose in his engine, leading to a sudden loss of power on Sunday.

Team-mate Nico Rosberg ended up fourth to lie 41 points behind Hamilton in the drivers' standings.

Sebastian Vettel won the race to move within eight points of the second Mercedes driver.

It capped a woeful weekend for Hamilton, who earlier failed to earn a record-equalling eighth straight pole position and was seeking his eighth win of the year.

While he still enjoys a healthy lead in the standings, any more gremlins in the remaining six races, with a maximum of 150 points still available, could bring Rosberg and Vettel right back into the title race.

But the 30-year-old Briton said he had been driving well until the technical failure, and vowed to resume his hot run of form when he arrives at Japan's Suzuka circuit.

"It's still a long way to go and I know I lost some points (in Singapore) but I was fast and on form and I will make sure I bring that out to Suzuka to fight back," said Hamilton. He had won seven of the 12 races before Singapore and been on pole 11 times.

He added: "The race was going very well. For me, it felt like I was driving at my best in the race.

"I think I had the pace to win.

"I did everything."

Team principal Toto Wolff called it a "character-building" weekend after Vettel earlier loosened Mercedes' 23-race hold on pole, demonstrating their lack of pace.

The slow corners and short straights of Singapore do not play to the strengths of the Mercedes engine but Wolff said the race was a warning shot to his team.

"There were times in the race when the pace looked okay but the guys in front were managing their tyres too so we must be realistic about our level of performance at this circuit," he said.

"Now we need to analyse everything precisely, understand the wrong turn that we took this weekend to learn the right lessons and then close this chapter.

"One bad weekend does not overshadow our achievements so far this year but we know that there is no room for complacency after a weekend like this. We will aim to hit back strongly in Suzuka."

Ferrari's Vettel was surprised that Mercedes were not on top of their game in Singapore.

"I don't think anyone can give you an answer. Even them," he said.

"But they have to be the favourites going into Suzuka.

"If that is the turn of the page, I wouldn't mind but we can't expect that because they've a very competitive package."

Suzuka could see Jenson Button ending his 16-year career in Formula One after a disastrous season.

At 35, friends say the 2009 world champion believes he has nothing left to prove and faces only frustration ahead if he stays with the woeful McLaren-Honda partnership.

The Briton has a queue of offers already to compete in the burgeoning World Sportscars series.

He has refused to deny speculation that he will join Chris Evans in presenting the BBC's new Top Gear programme.

Ron Dennis, McLaren's chief executive, is keen for Button to stay but is said to have accepted his driver's decision.

AGENCE FRANCE-PRESSE, THE TIMES, LONDON