Lewis Hamilton completed a sweep of all three practices when he topped the times for Mercedes ahead of Sebastian Vettel in Saturday?s third and final session for the United States Grand Prix.
The 32-year-old Briton, hoping to clinch his fourth title this weekend, clocked a fastest lap of one minute and 34.478 seconds on a cloudy and windy morning at the Circuit of the Americas, outpacing his Ferrari rival by 0.092 seconds.
Hamilton can take the championship if he wins and Vettel fails to finish in the top five.
Hamilton?s Mercedes team-mate Valtteri Bottas was third quickest, but two-tenths off the pace, after a tricky session in which he was frequently fighting to retain control of his car.
His compatriot Kimi Raikkonen was fourth in the second Ferrari ahead of Dutchman Max Verstappen, who on Friday signed a new three-year contract with Red Bull, and Felipe Massa of Williams.
Verstappen faces a 15-place grid penalty for Sunday?s race after Red Bull installed new power unit parts in his car.
Nico Hulkenberg was seventh ahead of his new Renault team-mate Carlos Sainz, making his debut with the team after switching from Toro Rosso.
Australian Daniel Ricciardo endured a messy morning?s work on his way to ninth in the second Red Bull ahead of Sergio Perez of Force India.
Debutant Brendon Hartley, the first New Zealander in F1 for 33 years, wound up in a respectable 15th place in his Toro Rosso.
Like several other drivers, he faces a grid penalty ? in his case 25 places -- for Sunday?s race.
Verstappen will drop 15 places, Hulkenberg 20 and Stoffel Vandoorne of McLaren five places, all for similar installation of new power unit parts.
The session was affected by a heavy wind and closely contested, as expected, by Mercedes and Ferrari, with a brief pause in the action when a Virtual Safety Car was used while the track was cleared after Romain Grosjean went off and into a gravel trap at Turn 14.
© 2017 AFP