Globetrotting Melbourne jockey Craig Williams has confirmed he will be home for long enough to ride Cox Plate fancy Pierro in the big race.

Trainer Gai Waterhouse offered Williams the ride earlier this week and the pair have ironed out the details in the days since.

"I was pretty thrilled, really happy to be on him," Williams said.

Williams has only been booked to ride Pierro in the one race with regular jockey Nash Rawiller to handle him in his lead-up runs.

Rawiller will surrender the plum ride because he has no hope of making the 49.5kg the colt is to carry under the weight-for-age scale in the Cox Plate.

Williams said he had already been offered five other rides in the pinnacle race, one of them on an international entry.

The form jockey of last year's spring carnival with victories in the Cox Plate and Caulfield Cup, Williams missed the winning ride on Dunaden in the Melbourne Cup through suspension.

But he is making every effort to ensure he will be in the saddle should Dunaden run again this year.

Williams is booked to ride Dunaden in the Prix Foy, a traditional lead-up to the Prix de l'Arc de Triomphe, at Longchamp on September 16 which requires him to miss the Dato Tan Chin Nam Stakes meeting at Moonee Valley the day before.

Dunaden's program after the Prix Foy depends on his performance in that race.

Should he win it he will almost certainly run in the Arc with Williams to ride.

If not, he will most likely return to Melbourne to defend his Cup crown.