Shanghai - Sebastian Vettel fired a warning as he powered his Ferrari to the fastest time in first practice at the milestone Chinese Grand Prix in Shanghai on Friday.
For what will be the 1000th Formula One race, the four-time world champion clocked a best time of one minute 33.911 seconds, with Mercedes' reigning title-holder Lewis Hamilton 0.207 secs behind.
Third fastest was Vettel's young Ferrari team-mate Charles Leclerc, 0.256 secs off the pace, followed by Red Bull's Max Verstappen and Valtteri Bottas in the other Mercedes.
But the session belonged to Germany's Vettel, 31, who has been under pressure after a series of unforced errors stretching back to last season.
He has been struggling with the set-up of his Ferrari and admitted on Thursday that he was still not really at home in it.
Vettel finished fourth in the season-opening race in Melbourne and was then fifth in Bahrain, where he was eclipsed by team-mate Leclerc, who is 10 years his junior.
Vettel's opening Shanghai salvo was all the more impressive because the Ferraris were on the slower medium tyres in first practice.
The Chinese Grand Prix has one of the longest straights in Formula One, which will suit Ferrari's awesome pace.
Toto Wolff, Mercedes team principal, called Vettel's straight-line speed "frightening".
"We need to stretch ourselves and fight," said Wolff, adding that Ferrari were clearly ahead of the rest in Bahrain despite the Mercedes one-two of Hamilton and Bottas.
"Having a benchmark like that helps and motivates."
Leclerc, the supremely talented 21-year-old who led in Bahrain but finished third after his Ferrari lost power, struggled early on in practice before finding some rhythm.
The Monegasque locked his wheels in his opening run and was then told over the radio from his Ferrari team on a subsequent lap: "We need you to push a bit."
In warm Shanghai conditions and with a slight breeze, Racing Point's Lance Stroll took a minor spin, the Canadian's predominantly pink car shuddering down the track.
After two grands prix this season, Bottas leads his team-mate Hamilton by one point at the top of the standings, followed by Verstappen, Leclerc and Vettel.
CHINESE GRAND PRIX: PRACTICE 1
1. Sebastian Vettel (GER) Ferrari 1:33.911
2. Lewis Hamilton (GBR) Mercedes 1:34.118
3. Charles Leclerc (MON) Ferrari 1:34.167
4. Max Verstappen (NED) Red Bull 1:34.334
5. Valtteri Bottas (FIN) Mercedes 1:34.653
6. Daniel Ricciardo (AUS) Renault 1:35.239
7. Pierre Gasly (FRA) Red Bull 1:35.428
8. Daniil Kvyat (RUS) Toro Rosso 1:35.447
9. Lance Stroll (CAN) Racing Point 1:35.466
10. Romain Grosjean (FRA) Haas 1:35.507
11. Kevin Magnussen (DEN) Haas 1:35.517
12. Nico Hulkenberg (GER) Renault 1:35.591
13. Lando Norris (GBR) McLaren 1:35.631
14. Alexander Albon (THA) Toro Rosso 1:35.695
15. Kimi Raikkonen (FIN) Alfa Romeo Racing 1:35.729
16. Carlos Sainz Jr (ESP) McLaren 1:35.756
17. Sergio Perez (MEX) Racing Point 1:35.820
18. Robert Kubica (POL) Williams 1:36.847
19. George Russell (GBR) Williams 1:37.619
20. Antonio Giovinazzi (ITA) Alfa Romeo Racing-Ferrari 0.000