MotoGP world champion Marc Marquez delivered the perfect comeback from a chaotic performance in Argentina for an unbeaten sixth victory in a row in Sunday's Austin round.

Starting from fourth after a three-place grid penalty for obstructing Pol Espargaro in qualifying, the Repsol Honda overtook Andrea Iannone at the end of the back straight and - barring a brief lunge for the lead by the Suzuki rider - was never headed.

The reigning four-time world champion later backed off to win by an advantage of 3.5s over Yamaha's Maverick Vinales, who claimed his first rostrum of the season. Iannone held on to third for a much-needed debut Suzuki podium from Vinales' team-mate Valentino Rossi.

The fight for fifth was the most closely contested of the race.

Argentina winner Cal Crutchlow fell from that battle, costing the Englishman the world championship lead. Instead, Ducati's Andrea Dovizioso moved back to the head of the standings, by a single point over Marquez, after a late pass for fifth on Monster Yamaha Tech3's Johann Zarco.

The bravest performance of the day, and indeed weekend, came from Repsol Honda's Dani Pedrosa, who rode to seventh despite fracturing his right wrist in Argentina.

Tito Rabat gave the Reale Avintia Ducati team further reason to cheer with eighth place, just ahead of fellow GP17 rider Jack Miller (Pramac). Miller's close turn one pass on fading factory rider Jorge Lorenzo also cost the Spaniard tenth place to Aprilia's Aleix Espargaro, who reached the finish for the first time this season.

Pramac's Danilo Petrucci also struggled badly on his GP18, finishing - like Lorenzo - over 30-seconds from Marquez.

KTM's Pol Espargaro, top rookie Takaaki Nakagami (LCR Honda) and Alvaro Bautista (Aspar Ducati) completed the point scorers.

Iannone's team-mate Alex Rins and Tech3's Hafizh Syahrin crashed out of the race in separate incidents, while Karel Abraham was forced to retire due to pain in his wrist from Saturday's big accident.

The opening European round of the season will be held at Jerez, Spain, on May 6.

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CLICK HERE for the new world championship standings...