Stoner now holds a 44-point lead in the championship standings

The Australian Ducati rider started from pole and was never troubled to beat Chris Vermeulen by 9.865 seconds.

Marco Melandri, who started from 10th, rode a superb race to finish third.

World champion Nicky Hayden, chasing three wins in a row at the track, failed to finish after being hampered by a first-lap clash with John Hopkins.

Stoner was in dominant form from the start and set a series of fastest laps, including a new track record, to build up an early lead over Dani Pedrosa, who had made a strong start.

Pedrosa saw his second place taken by Vermeulen by the fourth lap but Vermeulen was unable to challenge his Australian compatriot at the head of the field.

But there was plenty of action further back as Melandri, who rode with a dislocated left ankle, got involved in a battle with Pedrosa and Valentino Rossi for third place.

Melandri eventually moved past Pedrosa into third on lap 16 with Rossi also going past the Spaniard four laps later and the riders held their positions to the end.

Frenchman Randy de Puniet was sixth, just ahead of teammate Anthony West and Makoto Tamada.

British rider Chaz Davies, who now races in America, was given a wild card to ride for the D'Antin Ducati team in place of the injured Alex Hoffman, and finished a creditable 16th despite mechanical problems.

But there was nothing anybody could do to stop Stoner extending his lead in the championship to 44 points ahead of the summer break.

"The whole team did a great job," said the delighted Australian. "Now we can take a break and get ready for the second half of the season."

US MotoGP results
1 C Stoner (Aus) Ducati 44 minutes 20.325 seconds
2 C Vermeulen (Aus) Suzuki 44:30.190
3 M Melandri (Ita) Honda 44:45.966
4 V Rossi (Ita) Yamaha 44:50.989
5 D Pedrosa (Sp) Honda 44:55.947
6 R de Puniet (Fr) Kawasaki 44:58.631
7 A West (Aus) Kawasaki 45:01.747
8 M Tamada (Jpn) Yamaha 45:02.680
9 A Barros (Brz) Ducati 45:03.845
10 RL Hayden (US) Kawasaki 45:04.045