Lewis Hamilton saw off Mercedes team-mate Valtteri Bottas to finish fastest in second practice for the Spanish Grand Prix.
The world champion, who is bidding for a fifth consecutive win at Barcelona's Circuit de Catalunya, ended the concluding action of the day 0.139 seconds quicker than the Finn.
Hamilton's championship rival Max Verstappen was only ninth after he ran wide on his speediest lap.
Hamilton holds an eight-point advantage over Verstappen, and the British driver will be pleased with both his and Mercedes' form at the fourth round of the campaign.
Bottas topped the opening running in Barcelona before Hamilton assumed top spot in the afternoon.
While Verstappen split the Mercedes drivers in the first action of the weekend, the Dutchman returned to finish more than half-a-second adrift of the black machines.
The Red Bull driver, who is eight points behind Hamilton, made a slight error at Turn 10 and abandoned his lap.
Perhaps surprisingly, he did not attempt another quick time to hand Mercedes the advantage heading into the remainder of the weekend.
Indeed, on the early evidence of Friday's running, Verstappen and Red Bull will have to raise their game to take the fight to Mercedes at a circuit where the top 14 drivers were separated by less than one second.
Ferrari's Leclerc finished 0.165 sec behind Hamilton, with the Alpine pair of Esteban Ocon and Fernando Alonso line astern in fourth and fifth.
British driver Lando Norris ended the morning running in fourth but he had to settle for 12th later in the day, 0.922 sec off the pace.
Earlier, Nikita Mazepin and Robert Kubica both ran into trouble.
First, rookie Mazepin was in the gravel at turn eight within the opening minutes after he lost control of his Haas. The Russian was able to reverse away from danger before making it back to the pits.
Then, Kubica also found the sand trap, causing the session to be suspended.
The Alfa Romeo reserve driver lost control of his car by carrying too much speed through the new left-handed turn 10 before sliding backwards into the gravel.
The running was stopped for almost 10 minutes as the marshals cleared the Pole's car away from danger.
