It was a tale of two title hopefuls as Sebastian Vettel claimed the inaugural pole position at the Circuit of the Americas while Fernando Alonso was down in ninth.
Vettel had been the driver to beat heading into qualifying having topped all three practice sessions. And it was more of the same on Saturday afternoon.
The reigning World Champion posted a 1:35.657 to beat Lewis Hamilton to the coveted grid slot by a less-than-expected 0.109s.
Mark Webber will line-up third while Romain Grosjean qualified fourth but will drop down the order after a gearbox change penalty.
Abu Dhabi winner Kimi Raikkonen and Michael Schumacher were fifth and sixth while Championship hopeful Alonso could only manage ninth.
The Texan sun was beating down on the Circuit of the Americas with a really encouraging crowd of around 80,000 in attendance, many from Mexico and Venezuela. The ambient temperature was 20C and the track at 31C.
Romain Grosjean went into the session knowing that he had a five-place grid penalty from a gearbox change from FP3. Cars went out set up to run multiple laps with the front-runners using the Pirelli hard tyre and some of the new teams going with the medium right from the start. Also using mediums were Romain Grosjean and Paul diResta, whose cousin Dario Franchitti was one of the many American drivers in attendance.
Kimi Raikkonen set the first meaningful P1 at 1:41.058. This was hacked into by team-mate Grosjean with a 1:39.078 which he subsequently reduced to a 1:37.865. Bruno Senna popped up at the top of the timesheets with a 1:37.850, but then Grosjean reclaimed his place back with a 1:37.486. Felipe Massa, who looked quicker than Alonso for most of qualifying, slotted into P2.
Sebastian Vettel, who had been fastest in all three practices then set the new benchmark at 1:37.165 with Mark Webber slotting into P2 and Pastor Maldonado taking P3. Such was the nature of the diminishing fuel load and the lack of wear on the tyres that cars could continually circulate - like a Formula Ford qualifying session - with the times getting quicker and quicker and few coming back down the pitlane.
Some drivers gave their tyres a slow lap breather while a few hammered on round. Coming into the final three minutes the danger positions were: 15.Perez, 16.Kobayashi, 17.Rosberg, 18. Ricciardo,19.Glock, 20.Pic, 21.Kovalainen, 22.de la Rosa, 23.Karthikeyan, 24.Petrov.
As times continued to fall, Narain Karthikeyan dumped his HRT off track at Turn 2 bringing out the yellow flags. This left Nico Rosberg in a tricky position because he'd slipped back to P18 and couldn't improve in the first sector. Round came the Mercedes and he eased off to go a tenth of a second slower in S1 and then set personal bests in S2 and S3, he scraped forward to P17. Daniel Ricciardo couldn't improve.
Lewis Hamilton, meanwhile was having fun with P1 and took it down to 1:37.058, before Vettel annihilated that with a 1:36.558.
Petrov improved to P21 beating his team-mate Kovalainen (who said he was blocked) but not the two Marussias. Despite their pre-qualifying worries, HRT were well inside the 107% time.
So as the Texan dust settled out went: 18.Ricciardo, 19.Glock, 20.Pic, 21.Petrov, 22.Kovalainen, 23.de la Rosa, 24.Karthikeyan.
It had been a tremendous result for the non-KERS using Marussia team who had beaten the KERS-equipped Caterhams. It was also a tremendous result for the spectators who had seen 8 laps from Vettel instead of the usual 3 or 4 and 12 laps from Grosjean.
The multiple lappery of Q1 was going to be repeated in Q2 but with everyone on the medium tyre. Kimi Raikkonen was out early again setting the benchmark time at 1:37.672. He came round again and lowered it to 1:37.457.
Lewis Hamilton then gave another indication that Vettel might have a real fight on his hands for pole with a 1:36.795 lap which Mark Webber could not beat. Vettel could, though, with a breathtaking 1:35.971.
Times were falling fast as the fuel loads came down again and at the four-minutes-to-go mark the danger zone was: 7.Raikkonen, 8.Button, 9.DiResta, 10.Schumacher, 11.Senna, 12.Grosjean, 13.Vergne, 14.Alonso, 15.Rosberg, 16.Kobayashi, 17.Perez
At least that was an order for a few seconds as drivers improved radically. One person who wasn't going to improve at all was Jenson Button who radioed that he had lost power and cruised back to the pits, his engine still running. Alonso jumped to P4 pushing Jenson to P9 and when Grosjean grabbed P6 he was down to P10. Then Michael Schumacher administered the coup de grace by claiming P5, pushing Button to P11, which became P12 seconds later when Hulkenberg jumped into the top ten.
Interestingly the two Ferraris circulated round and while Massa improved to P2, Alonso could only stay P7.
So out went: 11.Senna, 12.Button, 13.DiResta, 14.Vergne, 15.Perez, 16.Kobayashi, 17.Rosberg
It had been another miserable session for McLaren, let down by another mechanical failure. However the biggest contrast in fortunes had been with Nico Rosberg who could not get a lap out his Mercedes while his team-mate was a mighty 1.4 seconds quicker.
As for the South American contingent at Austin, the Mexicans were despondent, but the Venezuelans were still in the contest.
The advice to drivers must have been to put in a slow first lap before going for a time, and so Alonso, Massa and Hamilton all did 1:42s and 1:43s first time round the block. Nobody had told this to Romain Grosjean who took provisional pole with a 1:37.227.
It was the same for Red Bull's Mark Webber who went straight for a time and took P1 with a 1:36.845. Lewis Hamilton responded with a 1:36.209, while Vettel - not surprisingly - trumped them both with a 1:35.877.
With two minutes of the session to run the order was: 1.Vettel, 1.Hamilton, 3.Webber, 4.Grosjean, 5.Raikkonen, 6.Schumacher, 7.Alonso, 8, Maldonado, 9.Massa, 10.Hulkenberg
Schumacher was trying his hardest and in the process went off at the tricky Turn 19 which had caught out Maldonado earlier. Hulkenberg jumped to P6. Lewis set the fastest middle sector on his way to a 1:35.928 - closing in on Vettel, but not close enough. Yet.
Alonso improved to P7 and was then pushed down again when Massa took P4. Schumacher hurdled back past them into P5. Vettel then made his pole safer with a 1:35.657 and Lewis came up just short with a 1:35.766 - fractions away from a big upset.
So, a grid of Vettel, Hamilton, Webber, Raikkonen, Schumacher and Massa in the front three rows. Grosjean was P4, faster than his Lotus team-mate, but takes a penalty.
Fernando Alonso ended up in a pretty miserable P9, faster than just Maldonado, although with Grosjean moving back to P9 with his gearbox penalty that will leave him in P8 but on the dirty side of the grid. It is widely anticipated that those on even numbers, on the dirty side, will suffer with poor grip at the start tomorrow.
It might even cross Ferrari's mind to change Massa's gearbox and move him back five places, so that Alonso can start both higher and on the clean side of the grid. With Button qualifying disastrously their constructors' battle with McLaren is almost won.
Whatever the case it is going to be hard work for Alonso to keep the championship alive tomorrow starting behind Vettel, Hamilton, Webber and Raikkonen. But if anybody can do it...
01. Sebastian Vettel Red Bull-Renault 1m35.657
02. Lewis Hamilton McLaren-Mercedes 1m35.766
03. Mark Webber Red Bull-Renault 1m36.174
04. Romain Grosjean Lotus-Renault 1m36.587
05. Kimi Raikkonen Lotus-Renault 1m36.708
06. Michael Schumacher Mercedes 1m36.794
07. Felipe Massa Ferrari 1m36.937
08. Nico Hulkenberg Force India-Mercedes 1m37.141
09. Fernando Alonso Ferrari 1m37.300
10. Pastor Maldonado Williams-Renault 1m37.842
11. Bruno Senna Williams-Renault 1m37.604
12. Jenson Button McLaren-Mercedes 1m37.616
13. Paul di Resta Force India-Mercedes 1m37.665
14. Jean-Eric Vergne Toro Rosso-Ferrari 1m37.879
15. Sergio Perez Sauber-Ferrari 1m38.206
16. Kamui Kobayashi Sauber-Ferrari 1m38.437
17. Nico Rosberg Mercedes 1m38.501
18. Daniel Ricciardo Toro Rosso-Ferrari 1m39.114
19. Timo Glock Marussia-Cosworth 1m40.056
20. Charles Pic Marussia-Cosworth 1m40.664
21. Vitaly Petrov Caterham-Renault 1m40.809
22. Heikki Kovalainen Caterham-Renault 1m41.166
23. Pedro de la Rosa HRT-Cosworth 1m42.011
24. Narain Karthikeyan HRT-Cosworth 1m42.740
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