Red Bull's Max Verstappen fired a warning on Saturday by going quickest in final practice for the Singapore Grand Prix, just 0.17 seconds ahead of championship leader Oscar Piastri.
.gif)
The Mercedes of George Russell and Kimi Antonelli were third and fourth, with Piastri's McLaren teammate Lando Norris fifth fastest at the Marina Bay Street Circuit.
There was little to choose between the top five, who were separated by less than one tenth of a second before qualifying under floodlights later on Saturday.
Four-time world champion Verstappen topped the timesheets with a lap of 1min 30.148sec.
The Dutchman won the previous two Grand Prixs, in Monza and Baku, and is challenging the season-long dominance of the McLarens at the top of the standings.
A maiden victory in Singapore for the Red Bull driver would keep him in the hunt for a fifth consecutive world title, having closed the gap from Piastri to 69 points and to 44 points on Norris.
McLaren are looking to wrap up the constructors' championship this weekend, where a podium finish for one of their cars will ensure a second consecutive title with six races to spare.
Liam Lawson has endured a torrid weekend so far on the unforgiving street layout.
The New Zealander crashed for the second successive session, losing control over a kerb at turn seven and ploughing his RB into a wall to bring out the red flags.
"I don't know what happened," Lawson said on team radio.
Lewis Hamilton finished eighth in FP3 but was to be investigated after the session for a red flag infringement, which could potentially cost the Ferrari driver a grid penalty for Sunday's race.
Carlos Sainz was sixth fastest in his Williams then came Isack Hadjar's RB.
Nico Hulkenberg's Sauber and the Ferrari of Charles Leclerc rounded out the top 10 on the timesheets.
Sunday's race in tropical Singapore has been declared the first official Formula One "Heat Hazard" with temperatures during the grand prix predicted to be 31C or higher.
That means all drivers must have liquid-cooled vests and refrigerant pump equipment available, though wearing them is not mandatory.
Many drivers were seen trying out the vests and their associated maze of cooling tubes under their fireproof overalls.