"It's a great result. I didn't really expect to have such an achievement," said Rossi.

Stoner, who started from second on the grid, got off to a perfect start and led fellow Australian and pole-starter Chris Vermeulen into the first croner, before setting up a commanding lead.

Stoner, on his Ducati, was soon followed by American John Hopkins, who failed to exert much pressure on the Australian, before Rossi passed the American just before the halfway mark and set off in pursuit of the leader.

The battle for victory raged with Rossi hounding Stoner until lap 23 of 26 when he passed the 22-year-old on a long corner and comfortably eased away to reignite his championship bid.

American reigning champion Nicky Hayden was third for Honda in his best finish of a thus far disappointing season.

Still no pole winners

After starting in the number one spot on the grid Vermeulen ended up finishing 16th after a crash with France's Randy de Puniet with 15 laps to go

None of the MotoGP races this year have been won from pole position.

Stoner now leads Rossi by just 19 points at the top of the championship standings at the half-way stage of the 18-leg world championship series.

"It's not a slim margin by any means against a rider of Casey's caliber," Rossi said of the championship race.

"But if we succeed in improving the motorcycle and above all the tyres, everything remains possible."