The American Suzuki rider had hoped to wait until after the race, when the world championship takes a four-week break.

But, after struggling in pain all season, Roberts has decided to correct the problem in order to return in good shape when the season resumes.

He said: "I've had problems ever since I started riding the four-strokes. The bike is heavier and takes more muscling around.

"We planned to have the operation done quietly during the summer break.

"After discussions with the team and the factory we decided it would be better to go ahead with the surgery directly.

"The usual recovery time is three to five weeks, but this will give us a little longer.

"I had to have it done anyway. The main thing is to get fit for when the season starts again.

After the break, the championship resumes with the Czech MotoGP at Brno on 25 August.