SOCHI, Russia (AP) Formula One leader Nico Rosberg took pole position for the Russian Grand Prix while Mercedes teammate Lewis Hamilton was 10th after another car failure ended his qualifying session early on Saturday.
With Rosberg leading the standings by 36 points, Sunday's race offers the German a chance to take the title race farther out of the defending champion's reach in just the fourth race of the season.
Rosberg and Hamilton traded fastest times in the first two sessions, far ahead of the competition, but their contest ended abruptly with a repeat of the power unit problem that left Hamilton at the back of the grid for the last race in China.
''It's not easy but there's nothing you can do about it. I'm doing everything I can,'' Hamilton said.
''Honestly, I'm just hoping to have a clean first lap and have a car in one piece to be able to fight with people. I've not had one race this year with a full car after turn one, so that's what I'm hoping for.''
Hamilton added he was ''very, very curious'' about what went wrong on Saturday, and has asked for ''as much detail as possible'' from the team.
Team principal Toto Wolff said the problem was a ''freak failure'' caused by an overheating component in the car's energy recovery system. Team staff thought they understood the problem after the failure in China, ''and here we go again, the same thing happens,'' Wolff said. ''We need to find out if we have really identified the root cause.''
Hamilton also received a reprimand from the stewards for disobeying instructions about driving across the run-off area.
With Hamilton out of contention, Rosberg secured pole with ease, opting not to run at the end of the final session after setting a time well beyond the reach of Ferrari's Sebastian Vettel, who was .706 seconds off the pace in second.
''I didn't know what Lewis had until now. I was just focused on myself out there, really going for it, and feeling great about it,'' Rosberg said.
Vettel also faces a five-place grid penalty for Sunday's race due to a gearbox change, meaning Valtteri Bottas of Williams will start on the front row after qualifying third, 1.119 seconds behind Rosberg.
The gulf in performance between Mercedes and its closest rival Ferrari leaves Rosberg with little opposition on Sunday, when he will seek his seventh race win in succession and fourth of the season.
''The others have been unfortunate today, extremely unfortunate, so that makes my race a little bit easier tomorrow, but an F1 race is never easy,'' Rosberg said. He added: ''The way the grid is, it does help me out a lot, for sure, to get the win tomorrow.''
Vettel admitted there was a big gap to Mercedes but insisted Ferrari could still challenge on Sunday. ''It's a long race, it's a long way, especially around here there's a lot of things that can happen,'' he said.
Ferrari's Kimi Raikkonen was fourth in qualifying, followed by Bottas' Williams teammate, Felipe Massa, and Red Bull's Daniel Ricciardo.
Australian Ricciardo had an unpleasant surprise in the second session when his wing mirror broke and flapped in front of him, obstructing his view, before eventually coming off the car altogether.
His Red Bull teammate Daniil Kvyat struggled at his home race, barely scraping into the third session and then qualifying eighth, partly thanks to Hamilton's car problem.
Both McLarens failed to reach the third session, with Jenson Button qualifying 12th and Fernando Alonso 14th.