By Alan Baldwin
SOCHI, Russia (Reuters) - Nico Rosberg seized pole position for the Russian Formula One Grand Prix on Saturday with world champion Lewis Hamilton joining his team mate on the front row in a perfect qualifying for Mercedes.
The pole was Rosberg's third of the season with championship leader Hamilton, who is 48 points clear of the German with five races remaining, denied his 50th for the third race in succession.
Hamilton, who had hoped for his 12th pole in 15 races, aborted his second and final lap of the final phase after making a mistake on a clear afternoon in the Olympic Park.
The front-row lockout was still just what Mercedes had ordered, with the team needing to score three points more than Ferrari to clinch their second successive constructors' title this weekend.
Finland's Valtteri Bottas qualified third for Mercedes-powered Williams with Ferrari's Sebastian Vettel and Kimi Raikkonen fourth and fifth.
Hamilton won last year's inaugural race in Russia from pole, with Rosberg runner-up after also starting on the front row, but he could not get close to Rosberg's time of one minute 37.113 seconds.
"We didn't get much practice but qualifying worked out really well and a good balance on the car," said the German after his second pole in a row and 18th of his career. "We had to guess a little bit...it all worked out well, I felt comfortable.
"Of course, the constructors' championship is a really important target for us this weekend, it would be amazing to clinch it for a second time so early on in the season, and so we are out to do that.
"At the same time of course I'm out here to reduce the gap to Lewis in terms of points."
Saturday's final practice was halted after just 35 minutes when Toro Rosso's Spaniard Carlos Sainz, who remained in hospital during qualifying and is doubtful for the race despite escaping serious injury, crashed heavily.
That accident also raised safety concerns, with the energy-absorbing barriers ending up on top of Sainz's car.
Friday's two sessions, on a track that skirts around the 2014 Winter Olympic venues, were also limited due to a diesel spillage in the morning and rain through the afternoon.
"A difficult weekend I think for everyone but I think I did a great job with this lap," said Hamilton. "I'm perfectly happy with the balance that I had.
"I think it's great for the team. As you saw last year, this is actually not such a bad race from P2 (second on the grid)."
Rosberg got alongside Hamilton at the start last year but made a mistake that sent him back to 20th place. The German then did 52 laps on one set of tires and fought back to finish second.
Bottas set the fastest lap in that race and said it was good to be right behind the Mercedes pair, even if Brazilian team mate Felipe Massa qualified only 15th.
Vettel had hoped for third place on the grid and felt sure the race would be closer.
"I believe we have a very good car so it should be a good race: I’m actually very confident for tomorrow," said the German.
"I think they (Mercedes) have been more or less one second away but I also think tomorrow it will be a lot closer, I expect that the gap will be smaller, we’ll see what we can do."
Behind the Ferraris, Force India's Nico Hulkenberg and Sergio Perez qualified sixth and seventh with Romain Grosjean eighth for Lotus and Sainz's team mate Max Verstappen ninth.
There was disappointment for Russian fans with the only home-grown driver, Red Bull's Daniil Kvyat, set to start in 11th place with Australian team mate Daniel Ricciardo 10th.
"I will fight hard and hope to finish in the points, which would be a good result," said Kvyat.
(Editing by Ed Osmond)