BARCELONA - A supremely-relaxed Lewis Hamilton delivered when it mattered on Saturday by producing a lap of searing speed to claim his fourth pole position of the season as Mercedes swept the front row for Sunday's Spanish Grand Prix. In the final seconds of a closely-fought qualifying session, the 2008 world champion clocked a majestic fastest lap in one minute and 25.232 seconds to outpace team-mate Nico Rosberg by 0.168 seconds.Rosberg had been fastest in the morning's final free practice session and led the way through both Q1 and Q2 before Hamilton found the extra pace required. It was his first pole in Spain and the 35th of his career. Only Vettel on 45 poles, Ayrton Senna on 65 and Michael Schumacher on 68 have claimed more. "It's been a tough day," said Hamilton. "Nico has been driving really well through P3 and qualifying, so I didn't know if I could get it. At the end, I had to eke out everything and more from the car."Coming here this weekend, I didn't know where everyone would be, but I see the development, and work that has gone on, to get the car ready and it inspires me. A big thank you to the team. To have the kind of performance we have, I have never really known that before. I'm overwhelmed -- so happy." His friend and team-mate Nico Rosberg did nothing to hide his feelings. "Yes, for me, it's very disappointing," he said. "I don't particularly enjoy coming second to Lewis. In the end, it was a good lap. Lewis just did a better job, but it's still all to play for tomorrow."Second is only a little away from optimum. All it takes is a good start tomorrow and I'm in the lead again and it's still all to play for." On a track where eight of the last 10 races have been won from pole and 21 of the last 23 from the front row, Hamilton's success made him favourite to extend his winning streak to four in a row and take over as championship leader from Rosberg. It was the second Mercedes one-two of the season and a reversal of the positions for last year's race.Australian Daniel Ricciardo took third on the grid for Red Bull after his team-mate and defending four-time world champion Sebastian Vettel qualified only 10th after suffering a drive failure early in the final session. Ricciardo, however, was disappointed. He said: "I think we did OK today, but it's not quite good enough. We're a second off - I expected a closer gap than that. "We've made improvements this weekend, but so have Mercedes. We're a clear third today and that's not bad, but we want to be closer to the top two."Vettel explained why he retired without recording a time in Q3. "I left the garage and lost second gear," he said. "It was clear there was a problem, but I still had third gear and above so I thought I'd try without second gear. But by Turn One, I'd lost all the other gears. It was a tricky day today. The track is very slippery out there. It's very close after Mercedes, I think, but I needed more and more laps."I was getting in a rhythm and I thought I could be shooting for P3. I think we have that in the car, but we never got that far." Valtteri Bottas qualified fourth for a resurgent Williams team ahead of Romain Grosjean of Lotus and Kimi Raikkonen in the leading Ferrari. Fernando Alonso was seventh in the second Ferrari, Jenson Button was eighth for McLaren and Felipe Massa ninth in the second Williams ahead of Vettel.