Mercedes driver Lewis Hamilton, of Britain, crosses the finish line to win the world championship and a victory at the Formula One US Grand Prix auto race at the Circuit of the Americas, Sunday, Oct. 25, 2015, in Austin, Texas. [Photo/Agencies]

REALLY TOUGH

Before the podium ceremony, Hamilton tossed his team mate a cap to wear. The German threw it back in disgust. No words were necessary.

"I don't know what happened," he said later when asked about his slip. "It was my race to win, but with some strange mistake that has never happened to me that was really disappointing.

"It's unbelievable. That was really, really tough at the time, to lose the win."

The victory, on a rollercoaster afternoon of enthralling racing, was Hamilton's third in four grands prix held in Austin and made the 30-year-old the first driver to win 10 or more races in successive seasons.

He was also only the second Briton since Jackie Stewart in 1973 to win three titles.

But for much of the race, on a drying track after torrential rain forced qualifying to be postponed from Saturday to Sunday monring, it had looked as if Hamilton would be kept waiting to realize his dream.

He had seized the lead at the start from second place on the grid, banging wheels with Rosberg at the first corner and forcing his team mate wide and down to fourth place.

Hamilton could not pull away from the chasing Red Bulls however, with Australian Daniel Ricciardo taking the lead with 15 laps gone and before drivers pitted from intermediate to slick tyres.

The Briton then dropped down to fourth place, with Rosberg back in the lead after 22 laps following the pitstops, but the first of two safety car deployments brought everything back into play.

Rosberg was heading for victory when, seven laps from the end, he made an unforced error, ran wide at turn 12, and Hamilton -- on fresher tyres after a later pitstop -- seized his opportunity.

Ricciardo had dropped back by then after colliding with the Force India of Nico Hulkenberg on a rare afternoon of mayhem with just 12 finishers.

One of them was American Alexander Rossi, the first home driver to compete in a US Grand Prix since 2007, in last place for Manor Marussia.

There was also early carnage when the two Saubers collided in the Swiss team's 400th race while the Williams of Felipe Massa spun after a coming together with Fernando Alonso's McLaren.

Russian Daniil Kvyat, who had also challenged for the lead in the early stages, brought out the crucial second safety car when he lost control and slewed across the track and into the barriers on the 43rd lap.

That gave Hamilton the chance to close right up and pounce when Rosberg erred.

Dutch teenage rookie Max Verstappen was fourth for Toro Rosso after a lively battle against both Ferrari drivers and Mexican Sergio Perez, whose country returns to the calendar for the first time in 23 years next weekend, was fifth for Force India.

Britain's Jenson Button produced some much-needed points for McLaren in sixth.