Ferrari’s Sebastian Vettel headed the Mercedes in final practice at the Australian Grand Prix.
The four-time champion was 0.479 seconds clear of Valtteri Bottas as Ferrari finally appeared to show the pace that had impressed pre-season.
Lewis Hamilton was third, 0.011secs behind his team-mate.
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It was far from a definitive read on performance, however, as a crash for Williams driver Lance Stroll ended the session 10 minutes early.
The Canadian rookie lost control at Turn Nine, badly damaging the car and bringing out the red flag.
It meant Mercedes, who were comfortably quicker than Ferrari in Friday practice, did not have time to go out and do a final pre-qualifying simulation run.
Hamilton and Mercedes expressed surprise at their advantage over Ferrari on the first day of running of the new season, having been convinced by their rival’s pace in testing that they faced a major challenge in 2017.
Instead, Hamilton was quickest by half a second and was a second clear of the Ferraris on average on his race simulation run.
Vettel had complained of a poor balance on Friday but the Ferrari looked hooked up throughout a much stronger performance on Saturday.
Ferrari’s Kimi Raikkonen was fourth quickest, 0.608secs behind Vettel. The red flag meant the two Ferrari drivers were out of the cars being introduced to movie star Nicole Kidman as the session came to a close.
The premature ending means qualifying at 06:00 GMT is even more intriguing than it always is at the start of the season, because there has been so little chance to judge the relative pace of the cars.
Nico Hulkenberg was an impressive fifth in the Renault, ahead of Red Bull’s Daniel Ricciardo, whose team have struggled with car behaviour throughout the weekend.
Ricciardo’s team-mate Max Verstappen was down in 12th place, complaining of poor balance.
There was a new driver in the Sauber, after Pascal Wehrlein pulled out saying he felt he lacked the fitness to perform at his best in the race.
The German was replaced by Ferrari third driver Antonio Giovinazzi, who was 20th and last and just over a second slower than team-mate Marcus Ericsson.
The McLarens of Fernando Alonso and Stoffel Vandoorne were 14th and 15th as they embark on what they have admitted will be a difficult season because of the poor performance of their Honda engine.