Title in sight: Lewis Hamilton celebrates pole position.
Hamilton has broken down barriers as Formula One's first and only mixed-race champion, and did so coming from an under-privileged background without wealth or any family history of motor racing.
Ferrari's Kimi Raikkonen will start second and Mercedes' Vallteri Bottas will start third.
Esteban Ocon was an impressive sixth for Force India ahead of Nico Hulkenberg of Renault, Romain Grosjean of Haas, Charles Leclerc of Sauber and Sergio Perez in the second Force India.
"I think he's a great guy and we talk a lot, much more than I expected", he said.
Vettel, who swore over the radio in frustration after discovering he had lost to Hamilton, added: "It was a bit of a shame that we missed out by that little time". It was going to require solid laps. "But I was pretty happy with the laps I had".
"So I am just focusing on driving the best that I've driven all year long and that we get the auto where we need to get it". "It's been a pretty positive day". "We are focusing on making sure we deliver. We will try tomorrow and it will be interesting".
More rain is forecast for final practice and qualifying.
Mercedes did not appear to have the pace to beat Ferrari following the early phases at a cold and blustery Circuit of the Americas. If there is a auto right behind you, it might run into you.
Vettel was backed up by other drivers as well, with Gasly's Toro Rosso team-mate Brendon Hartley sympathising on the grounds that slowing down to make the delta can be hard to manage safely.
Hamilton climbed out of his Mercedes to greet film star Matthew McConaughey with a hug before returning to the fray, a clear signal of his relaxed mood.
"It looked like the Ferrari had an advantage on straight-line speed - yes, that again". The Dutchman's exit meant he was out-qualified by his team-mate Ricciardo for the first time in 12 outings.
Vettel finished 10th in the second practice session as title rival Lewis Hamilton comfortably led the way. While the awful weather that hit Austin during Friday practice means we had no chance to evaluate the relative performance of Mercedes and Ferrari on the day, the previous three weekends have proved emphatically that the silvers cars are the faster by some margin.