By Alan Baldwin
SOCHI, Russia (Reuters) - Formula One championship leader Nico Rosberg seized pole position for the Russian Grand Prix on Saturday after a power unit failure piled more misery on Mercedes team mate Lewis Hamilton.
The German, chasing his seventh successive win and fourth of the season, clinched one of the easiest poles of his career and will be joined on the front row by Finland's Valtteri Bottas in a Williams.
Ferrari's Sebastian Vettel qualified second but has a five-place grid penalty for an unscheduled gearbox change.
"I was quite confident that the lap was good enough," said Rosberg, whose best effort was a hefty 0.706 seconds faster than Vettel's.
"In Quali Two Ferrari (NYSE:RACE) was quite far away and I knew that Lewis was unable to participate in the last part of qualifying. I was very sure it was going to be enough," added the German, who also took pole last year in Sochi.
It was the 24th pole of Rosberg's career and the 40th in 42 races for champions Mercedes.
Hamilton, the triple world champion and winner in Russia for the past two years but 36 points behind Rosberg in a season full of setbacks, saw his luck desert him in qualifying for the second race in a row.
The Briton had been quickest on Friday and in final practice but was sidelined from the final 10-car showdown for pole when his car's power unit failed during the second phase.
He is set to start 10th, unless he collects any further penalties.
"It's the second engine I took at the last race and it's the same failure as the last race," said an unhappy Hamilton, who was also summoned to the stewards for failing to follow the race director's instructions at turn two.
In China two weeks ago Hamilton started from the back of the grid after he failed to set any lap time in qualifying due to a power unit failure.
The Briton, who took pole in the first two races of the season but then made slow starts, fought back to seventh in the race in Shanghai.
"It's a very bizarre situation," Mercedes motorsport head Toto Wolff told Sky Sports television. "It seems like the same failure as in Shanghai, which means we have to reassess the root cause of the failure.
"He seems to have all the bad luck and the other side of the garage has all the luck... It's getting tough for Lewis now and I have no doubt he will come out of it. But he has every right to be upset."
Ferrari's Kimi Raikkonen and Williams' Brazilian Felipe Massa will share the second row with Australian Daniel Ricciardo behind for Red Bull with Force India's Sergio Perez sixth.
Vettel starts in seventh place with Russian Daniil Kvyat, the Red Bull driver that the German accused in China of behaving like a 'madman' and overtaking 'like a torpedo' as the Ferraris collided, together on the fourth row.