After two difficult races, reigning MotoGP champion Casey Stoner clawed back some of the ground lost to title leader Jorge Lorenzo with a hard-earned victory in Sunday's US Grand Prix.

Stoner, who had dropped from being equal with Lorenzo after Assen to 37-points behind heading into Laguna Seca, began the race between Lorenzo and Dani Pedrosa on the front row.

Significantly Stoner made the brave decision to run the softer rear tyre, but any thoughts of trying to make an early break were instantly dashed as he slipped to third at turn one.

After taking several laps to pass Repsol Honda team-mate Pedrosa, Stoner then spent the middle stages of the race locked on Lorenzo's rear wheel.

It seemed that Lorenzo just needed to hold on and wait for Stoner's rear tyre to fade. Instead, the Australian perfectly balanced speed with smoothness and only got stronger.

Stoner overtook Lorenzo as they accelerated out of the final turn with ten of the 32 laps remaining, then rode to his third US GP win by 3.4s.

"It's been a difficult weekend for us in general especially trying to make the hard tyre work. So for the race I decided to go with the soft option and be a little more careful with the tyre, keep a little more traction and not spin so much," Stoner explained.

"At the beginning of the race I tried to move to the front but Dani and Jorge were riding very good lines and it was impossible to get past. I decided to slow the lap times a little and try to save the tyres until the end and then we could start to come back.

"I was confident for the entire race that I had enough pace for the win, we just needed to make sure the tyre would last until the end. When we got to the front we put in some good laps and pulled some small advantage and just continued from there.

"I'm very, very happy and a big thanks to all the team."

Stoner - who will retire at the end of 2012 - has now taken four wins this year (one less than Lorenzo) and closed to within nine points of Pedrosa.

Stoner is 32 points from Lorenzo with eight rounds remaining, starting at Indianapolis on August 17-19.