The Saudi Arabian Grand Prix is live on BBC Radio 5 Live and the BBC Sport websiteFerrari's Charles Leclerc headed Red Bull's Max Verstappen in first practice at the Saudi Arabian Grand Prix.
Their laps, separated by 0.116 seconds, were set on different compounds of tyres at opposite ends of the session.
Verstappen's time was set early in the session on the hardest compound while Leclerc was on soft tyres late on.
Leclerc was about 0.6secs off Verstappen when he ran the hard tyre on his first run. Alfa Romeo's Valtteri Bottas was third.
Ferrari's Carlos Sainz was fourth fastest, ahead of the Alpha Tauris of Pierre Gasly and Yuki Tsunoda.
Mercedes driver Lewis Hamilton was ninth fastest, complaining of aerodynamic "bouncing", the single biggest problem faced by the world champions so far in this new era of F1.
Leclerc won the first race of the season in Bahrain last weekend after a close fight with Verstappen, who retired from second place with three laps to go with a loss of fuel pressure.
Both Red Bulls retired with the same problem, which the team said was caused by a vacuum in the fuel system that prevented the pumps from drawing fuel.
"We've taken the necessary steps to correct this issue and we expect no problems this weekend," a statement said.
The first session in Saudi Arabia is expected to be unrepresentative of true form because it is run in daylight while qualifying and the race are held at night when conditions are cooler.
Leclerc and Verstappen were among a number of drivers who had off-track moments during the session, in which conditions were difficult because of wind on the Jeddah coastline.
Haas driver Kevin Magnussen, one of the stars of the first race of the season with fifth place on his return to F1 after a year away, failed to set a lap as a result of hydraulic problems with his car early in the session.
Alpine's Fernando Alonso, who was 10th fastest, has a new engine in this weekend after the team found a "suspected sealing issue" in the power-unit he used in Bahrain.
They said they expect the first engine to be put back into his pool of engines once it had been investigated back in Europe.
The second practice session is at 17:00 GMT.
