F1 testing: Vettel fastest on first morning, more trouble for McLaren

Vettel finally emerged on top of a duel with Mercedes' Valtteri Bottas to take Tuesday morning honours, with Max Verstappen ending up third-quickest for Red Bull.

Bottas got down to business straight away and was the benchmark for much of the morning, with a longer run on mediums getting his best down to 1m20.756s by the end of the opening hour.

He hit 24 laps, more than anyone else, just before Stoffel Vandoorne's stopped McLaren brought out the red flags.

Vandoorne, with one flying lap to his name, had just set personal best first and second sectors before coming to a halt exiting the final corner with a battery-related problem.

The McLaren remained in the garage until the very end of the session almost three hours later, when Vandoorne emerged in time for three exploration laps.

After the McLaren-induced stoppage ended Bottas and Vettel were quickly out on soft Pirellis, with Vettel briefly nabbing top spot on a 1m20.653s before Bottas reclaimed the place by just 0.022s.

Bottas nudged his benchmark down to a 1m20.596s and Verstappen improved to a 1m20.649s on medium tyres, with the top three teams separated by barely half a tenth at that stage.

With little more than half an hour to go Vettel ended a long run on mediums with the fastest lap of the session, a 1m20.396s, to move two tenths clear of Bottas.

Verstappen did not improve again and was third-fastest, falling one lap short of matching Vettel and Bottas on 86.

Behind the top three Pierre Gasly continued the Toro Rosso-Honda partnership's fine start to life with a soft-tyre lap half a second off the pace.

The Frenchman managed 53 laps as Honda continued to make hay while its old partner McLaren hits new troubles.

Kevin Magnussen was the final driver to lap within a second of Vettel's best, posting a 1m21.298s on soft tyres.

That put Haas just over a tenth clear of Renault, which kept Nico Hulkenberg in the garage for much of the first half of the morning.

However, long runs on the medium tyre helped the French manufacturer break for lunch with a reasonable tally of 48 laps.

Sergey Sirotkin was just a tenth back for Williams, which was a little short of running on 42 laps.

Marcus Ericsson used soft tyres to get Sauber ahead of Force India in the final 10 minutes of the session, 1.497s off the ultimate pace.

Force India sparked a second red flag mid-morning when Sergio Perez had a trip off-circuit exiting Turn 4 and brought gravel back onto the track, which was swiftly cleared by marshals.

Perez ended the morning with worst non-McLaren tally of 37 laps.

Day one morning times