Austin MotoGP: Marquez controversially beats Vinales to pole

Marquez predictably led the opening runs at the Austin, Texas track with a best lap of 2m04.134s, giving himself a 0.394s buffer over nearest challenger Valentino Rossi.

But the reigning champion lost the front end of his works Honda at Turn 13 mere moments later, forcing him to get a ride back to the pits to change to his second bike for the final part of the session.

On his out lap for his second run, Marquez blocked Vinales while the Yamaha rider was on a hot lap, touring on the racing line at Turn 15.

Vinales was forced to abandon his lap and gesticulated angrily at Marquez, but regrouped to grab the top spot with a 2m04.064s next time round.

Marquez well and truly obliterated that effort as he lapped in 2m03.658s, 0.406s up on Vinales - but as the session ended, it was announced the incident between the pair was under investigation.

Suzuki rider Andrea Iannone was best of the rest in third, 0.551s off the pace and one thousandth of a second ahead of Tech 3 Yamaha rider Johann Zarco.

The second works Yamaha of Rossi was fifth ahead of the lead Ducati of Jorge Lorenzo.

Points leader Cal Crutchlow (LCR Honda) was seventh ahead of Andrea Dovizioso (Ducati), an injured Dani Pedrosa (Honda) and Danilo Petrucci, one of two riders to advance from Q1.

Completing the top 12 were Alex Rins (Suzuki) and shock Q1 pacesetter Pol Espargaro.

Provisional starting grid