Yamaha's Lorenzo slowed by braking issue in Austin MotoGP race

Lorenzo started alongside Marquez on the front row of the grid, and led the field into Turn 1, only to overshoot slightly and run wide.

A repeat of the incident happened at Turn 11 later in the lap, handing Marquez a lead he would not relinquish.

By the time Lorenzo got past Andrea Dovizioso for second on lap five, Marquez was two seconds clear, and he had no answer to stem the time loss, let alone make inroads as the Honda rider claimed his fourth consecutive victory at the Circuit of the Americas.

"I had a lot of confidence from braking all weekend," Lorenzo said.

"But today with the hard rear tyre and the full tank I don't know what happened, but I couldn't stop the same.

"[It was] very bad, always with a lot of problems.

"That's why I make some mistakes, in the first corner, in some hairpins, trying to be in first position.

"I hoped to be faster, but today it was impossible.

"Every time I was slower and slower, so today was not the day to fight for the victory and I knew it from lap seven or eight, so I just needed to finish the race, get these points."

While Marquez's advantage got out to eight seconds at one point, he backed off at the end, to win by six seconds.

Lorenzo won the season opener in Qatar, but primarily due to crashing out in Argentina last weekend, returns to Europe 21 points behind Marquez in the standings.

"Today, like the last four years in this track, Marc made the difference," Lorenzo acknowledged.

"We couldn't stay with him."

ROSSI SURPRISED BY CRASH

Yamaha team-mate Valentino Rossi crashed out at Turn 2 on the third lap, having dropped to sixth early.

After his first DNF in 25 races - a stretch going back to the Aragon round in 2014 - Rossi admitted he did not know what had happened until the bike was "30 metres or more in front of me".

"At the start unfortunately I burnt the clutch," he said.

"I was third but the clutch slipped a lot, so I had to go slow to try and recover the clutch and I lost some positions.

"At the same time I was not so far [behind], I felt good with the bike, we worked well during the weekend and I felt fast.

"I had the feeling the clutch was coming back already but I entered Turn 2, I didn't feel from the bike I was too fast but looking at the result maybe I was."