Nico Rosberg broke free of Lewis Hamilton's stranglehold to seize his ninth pole position of the Formula One season when he topped qualifying for the American Grand Prix.
The 29-year-old German clocked a best lap of one minute and 36.067 seconds in the final moments to outpace Mercedes teammate and championship leader Hamilton by almost four-tenths of a second.
Until qualifying, Hamilton had reeled off fastest laps in all three practice sessions and demonstrated the speed and form that suggested he was in line for his fifth straight win and 10th this year in Sunday's 56-lap race.
But Rosberg, who is 17 points behind Hamilton with three races remaining, responded with a cool showing under pressure as he delivered laps that were faster that last year's pole time set by four-time champion Sebastian Vettel, who won last year's race for Red Bull.
"Great job guys," said Rosberg. "Thank you very much."
It was his 13th career pole and meant he had out-qualified Hamilton 10-7 over the season so far.
"It worked out really well. Together with my engineers, I arrived in qualifying with a car that I was really happy with for qualifying.
"This morning, the conditions were quite different so it wasn't easy to get everything right. First place today is awesome, but the race is what counts, so I need to fully focus on tomorrow."
Hamilton revealed that he had endured braking problems for two days.
"Nico did a great job," he said.
"I was struggling with braking. The left brake was always about 100 degrees less than the right and kept catching, no matter what I did."
Valtteri Bottas was third for Williams, the fifth time he has taken that position in the last seven race weekends, ahead of his team-mate Brazilian Felipe Massa.
"It was a pretty good qualifying again for me," said the Finn. "I'm pleased with two good laps in Q3 and happy to have locked out the second row for the team."
Australian Daniel Ricciardo was fifth for Red Bull ahead of two-time champion Fernando Alonso of Ferrari, the 2009 champion Jenson Button and his McLaren team-mate Kevin Magnussen.
Kimi Raikkonen was ninth in the second Ferrari and Adrian Sutil 10th for Sauber.
Vettel made only a token appearance in Q1 and qualified 17th for Red Bull, knowing he will start Sunday's race from the pit lane after a change of power unit.
Button will start from 12th place due to a five-place penalty for a gearbox change.
On another afternoon of sunshine, with the track temperature rising beyond 32 degrees, the opening Q1 mini-session was memorable for the departure of Vettel.
It was the first time in 94 races that the four-time champion had failed to progress to Q2 having chosen to make little more than a token appearance to conserve his power unit for the rest of the season.
Out with the German went Frenchman Jean-Eric Vergne, who was 15th for Toro Rosso, Mexican Esteban Gutierrez of Sauber who was 16th and Frenchman Romain Grosjean, 18th and last for Lotus.
That session saw Hamilton clock the best time ahead of Massa and Bottas, but the Briton required an extra set of tyres to do the job.
In Q2, Rosberg broke Hamilton's grip at last, going fastest early on in the mini-session and then, taking an extra set of tyres, delivering a sensational lap in 1:36.290.
It ended a run of 10 sessions dominated by Hamilton and left the Englishman second by nine-tenths.
The four men to miss the cut to the top ten shootout were Venezuelan Pastor Maldonado of Lotus in 11th place ahead of Mexican Sergio Perez and his Force India team-mate German Nico Hulkenberg and Russian Daniil Kvyat of Toro Rosso.