Series leader and world champion Lewis Hamilton narrowly topped the times for Mercedes in Saturday's final free practice session for Sunday's Bahrain Grand Prix.
The 30-year-old Briton was just 0.069 seconds clear of his nearest rival, four-time champion Sebastian Vettel of Ferrari, after a tense session in hot conditions at the Sakhir Circuit where the Italian team confirmed their potential to shine in the sizzling heat.
Hamilton's Mercedes team-mate Nico Rosberg was third ahead of Finn Kimi Raikkonen in the second Ferrari, but both were more than three-tenths adrift of the pace-setter.
In the dry and windy conditions, Hamilton set his best lap in the final minutes to set up the prospect of a competitive floodlit qualifying session later in the day when Mercedes are expected to improve their engines' and tyres' performance in the cooler conditions.
Behind Raikkonen, another Finn, Valtteri Bottas of Williams, was fifth-quickest ahead of his Williams team-mate Brazilian Felipe Massa, Venezuelan Pastor Maldonado of Lotus, Australian Daniel Ricciardo of Red Bull and German Nico Hulkenberg of Force India. Brazilian Felipe Nasr of Sauber completed the top 10.
The two struggling McLaren-Honda men, 2009 champion Jenson Button and two-time champion Fernando Alonso were down in 11th and 16th after another frustrating session interrupted by one red flag stoppage when Russian Daniil Kvyat spun into a gravel trap in his Red Bull car.