"We're very pleased," Vettel said ahead of the penultimate race of the season at the new Circuit of the Americas track. "It was extremely slippery to start with. The circuit is brand new and it takes a while to come in, but it was quite a lot of fun to slide a couple of corners.
"In the final section I would have loved to have gone a bit quicker. It was a bit closer than I wanted, but it's fantastic to start on the front and on the clean side."
If Vettel wins, Alonso must finish fourth or better to keep the championship alive until the final race of the season at Interlagos, Brazil next weekend.
If Vettel is second, Alonso must finish eighth and if the German is third, Alonso must be in the top 10.
Alonso had been fourth quickest in the morning's final practice session but he looked to be struggling throughout qualifying and was beaten by team-mate Felipe Massa, who qualified seventh, in all three sessions.
In qualifying, Hamilton looked as if he might have a chance of snatching pole but he fell just short on his final lap.
US Grand Prix qualifying - top three drivers
"I'm not really concerned about the first corner," said Hamilton. "I'm more concerned about being on the dirty side of grid. I did a launch there earlier and it was quite slippery.
"I don't want to get in the way of Sebastian's race but I do want to win."
Vettel's time was 0.517secs quicker than team-mate Mark Webber, who was third fastest.
Lotus's Kimi Raikkonen will start fourth ahead of Mercedes driver Michael Schumacher and Alonso's team-mate Felipe Massa.
Force India's Nico Hulkenberg, Alonso, the demoted Grosjean and Williams's Pastor Maldonado complete the top 10.
McLaren's Jenson Button failed to make it into the top 10 shoot-out when his car lost power in the second session and will start 12th ahead of Scot Paul di Resta's Force India and the Toro Rosso of Jean-Eric Vergne.
At the back of the grid, both Marussia drivers Timo Glock and Charles Pic beat their rivals from Caterham Vitaly Petrov and Heikki Kovalainen.
Although the cooler than expected temperatures in south Texas have meant the drivers are struggling for grip on the new track surface, there has been a positive reaction to the track that has been chosen to host the first US Grand Prix since 2007.
F1 is keen to establish itself in the American market and senior figures have said they feel this race can be a long-term success.
McLaren team boss Martin Whitmarsh said: "It's an enormously challenging circuit. We've got to make sure that as Formula 1 as a whole, we put on a show this weekend; that we reach out over the coming year and we build this into a fantastic event."
Qualifying top 10
1. Sebastian Vettel - Red Bull 1:35.657
2. Lewis Hamilton - McLaren 1:35.766
3. Mark Webber - Red Bull 1:36.174
4. Kimi Raikkonen - Lotus 1:36.708
5. Michael Schumacher - Mercedes 1:36.794
6. Felipe Massa - Ferrari 1:36.937
7. Nico Hulkenberg - Force India 1:37.141
8. Fernando Alonso - Ferrari 1:37.300
9. Romain Grosjean - Lotus 1:36.587
10. Pastor Maldonado - Williams 1:37.842
Romain Grosjean handed five-place grid penalty.
United States Grand Prix 2012, day two
Saturday, 17 November: Qualifying highlights; 21:00 GMT, BBC Two
United States Grand Prix 2012, day three
Sunday, 18 November: Race 18:55 GMT; 5 live and live text commentary online. Race highlights; 22:25 GMT BBC One
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