The United States Grand Prix is live on 5 Live and the BBC Sport websiteValtteri Bottas headed Lewis Hamilton as Mercedes set an imposing pace in first practice at the United States Grand Prix.
Bottas, who has a five-place grid penalty following an engine change, was 0.045 seconds quicker than Hamilton.
Hamilton's title rival Max Verstappen was a massive 0.932secs off the pace in his Red Bull, ahead of the Ferraris of Charles Leclerc and Carlos Sainz.
Leclerc had an off at the high-speed Esses but escaped damaging his car.
Mercedes' pace bodes well for Hamilton as the seven-time champion seeks to overturn Verstappen's six-point gap and reclaim the championship lead in Austin.
However, while Mercedes were expected to have a slight edge based on recent performance, the size of their advantage suggests there must be an off-set in engine mode or fuel load at play in the times, as the gap seems too big to be representative.
Mercedes have fitted Bottas' car with a sixth internal combustion engine - only three are permitted for the season - which means a five-place penalty for the Finn.
Williams driver George Russell and Aston Martin's Sebastian Vettel also have engine penalties but they have taken more components - a turbo and MGU-H as well as the ICE - and they will start from the back of the grid as a result.
Leclerc, who lost control on the exit of Turn Five through the bumpy and demanding first sector, was 0.5secs slower than the Red Bull.
Both drivers of the red car were struggling with oversteer in high-speed corners, the cause of Leclerc's incident.
Alpha Tauri's Pierre Gasly was sixth quickest ahead of the Red Bull of Sergio Perez, McLaren's Lando Norris, and the Alfa Romeos of Antonio Giovinazzi and Kimi Raikkonen, who had a spin at Turn Nine late in the session.
Ocon's team-mate Fernando Alonso caused an early red flag when his Alpine stopped on track leaking fluid on his first lap out of the pits.
The Spanish two-time world champion did get back out on track and ended the session 15th.
Mick Schumacher had a late incident with Perez, when the Red Bull dived for the inside at Turn 12 and the two collided, Schumacher's Haas bouncing into the run-off area.
