Sebastian Vettel issued an early warning to Fernando Alonso that he is not prepared for their title fight to go down to the wire.
In the opening practice session at the £250million Circuit of The Americas that plays host to the first United States Grand Prix for five years, Vettel left his rivals in the shade come the end.
The 25-year-old Red Bull star, who is currently 10 points clear of Alonso in the driver's championship, finished 1.418secs clear of Lewis Hamilton, the biggest margin at the end of any practice session this season, with Alonso 2.212secs adrift in his Ferrari.
It is, of course, still early days on a track still very green and needing to be rubbered in, but as a potential marker, it will have had an effect.
Vettel needs to finish 15 points clear of Alonso on Sunday to become only the third driver in Formula One history - Juan Manuel Fangio and Michael Schumacher the others - to claim three titles in a row.
The top three teams occupied the top six places, with Jenson Button in his McLaren, Red Bull's Mark Webber and Ferrari's Felipe Massa fourth, fifth and sixth respectively, all around 2.5secs down.
Force India's Nico Hulkenberg was the best of the rest ahead of Sauber's Kamui Kobayashi and team-mate Sergio Perez in eighth and 10th, with Nico Rosberg in his Mercedes splitting the Sauber duo.
Paul di Resta, apparently struggling badly with the balance of his Force India car, was 11th quickest, 3.658secs behind Vettel, and 0.8secs down on team-mate Hulkenberg.
The Lotus duo of Kimi Raikkonen, who gave the team their first win this season last time out in Abu Dhabi, and Romain Grosjean were a lowly 14th and 15th but with the prospect of more to come.
At the bottom, and clearly out of his depth on this occasion, was HRT reserve Ma Qing Hua, the Chinese finishing 10.434secs off the pace, and 1.7secs behind team-mate Pedro de la Rosa.