Carlos Sainz led Charles Leclerc in a Ferrari one-two in first practice at the Mexican Grand Prix as 0.2 seconds separated the top six drivers.
Sainz was 0.047 seconds ahead of his team-mate at the Autodromo Hermanos Rodriguez in Mexico City.
The Red Bulls of Sergio Perez and Max Verstappen were next, followed by Lewis Hamilton’s Mercedes and Fernando Alonso’s Alpine.
Verstappen had a spin at the Esses but managed to stay out of the barriers.
The world champion also had an oversteer moment at Turn Five later in the session as he struggled on the low-grip track.
Perez and Verstappen, who set identical times to the thousandth of a second, were 0.12secs behind Sainz, with Hamilton 0.142secs off the pace and Alonso 0.192secs behind.
Alfa Romeo’s Valtteri Bottas, McLaren’s Lando Norris, Alpha Tauri’s Pierre Gasly and Aston Martin’s Sebastian Vettel completed the top 10.
A number of teams used young drivers in the session to fulfil their obligations under the rules.
The quickest was Liam Lawson in the Alpha Tauri in 16th place, followed by Williams’ Logan Sargeant, Mercedes’ Nick De Vries, Alpine’s Mick Doohan and Haas driver Pietro Fittipaldi.
Lawson, Doohan and Fittipaldi all had their sessions curtailed by technical problems.
Both Fittialdi’s and Lawson’s issues led to the session being stopped, and Lawson’s was close enough to the end of the hour for it not to be resumed.
The second session, which starts at 22:00 UK time and runs for 90 minutes, will be devoted to testing 2023 Pirelli tyres, as was the case in Austin last weekend.
