Mercedes will start the Spanish Grand Prix from the front row after Nico Rosberg had the fastest qualifying time ahead of teammate Lewis Hamilton on Saturday.
While Hamilton had the fastest times in the first two qualifying sessions, Rosberg edged him to win the pole position in 1 minute, 20.718 seconds.
''The race is very long, and to win it's not good enough to start from pole - you still have to have the fastest race car,'' said Rosberg, who finished ninth in Bahrain after winning pole. ''I'm a little bit more confident for tomorrow, but the race is going to be a completely different thing.''
Three-time defending champion Sebastian Vettel will start from third spot for Red Bull ahead of Kimi Raikkonen's Lotus.
''I'm quite happy to be honest because yesterday and this morning I wasn't really happy. We improved the car and things calmed down,'' Vettel said. ''It's a tough challenge and the tires don't last as well as we would like.''
The degradation of the Pirelli tires has been an issue all season, and drivers are still largely unhappy at how quickly they wear out.
Ferrari has yet to secure a pole position this season, and it proved to be another frustrating afternoon after fast practice times in the morning. Fernando Alonso will start fifth and Felipe Massa sixth,
Jenson Button failed to make the cut for the third session. The Briton will start in 14th place, with teammate Sergio Perez in ninth spot.
Massa had been fastest in the third and final practice session, edging Raikkonen by .006 seconds. Red Bull driver Mark Webber was third but he had a poor qualifying session and will start from eighth place, behind Lotus' Romain Grosjean.
Following three frustrating seasons, Ferrari wants its drivers to find extra speed in qualifying to increase the pressure on Red Bull.
The closest Ferrari has been to pole was when Massa qualified second at the Malaysian GP in March. Alonso started the previous three races from third spot on the grid, but Saturday's run will have left home fans on the Circuit de Catalunya feeling disappointed.
Mercedes has been fast but lacking durability this season, so Hamilton and Rosberg stayed on longer runs than other drivers in practice.
