PARIS (AP) - Epsom Derby winner Workforce upset favorite Behkabad to win Sunday's Prix de l'Arc de Triomphe, Europe's richest horse race.

The 3-year-old colt, ridden by Ryan Moore, held off a strong challenge from Nakayama Festa on the home stretch.

``He was back to his best today and we got a nice run through,'' Moore said. ``There was half a gap there and he was very brave and really quickened into it well.''

Workforce gave trainer Sir Michael Stoute his first win at the Prix de l'Arc. It also was Moore's first triumph in the prestigious race held at the Hippodrome de Longchamp in Paris' Bois de Boulogne.

Sarafina finished third and Behkabad was fourth.

Workforce was only given the go-ahead to race after a final training run Thursday following a disappointing showing at the King George VI and Queen Elizabeth Stakes in his previous outing.

``If you have any ambition when you start training, you want to win the Arc,'' Stoute said. ``We have had a lot of horses running particularly well in it without doing it, so I'm thrilled.''

The field was reduced to 19 when Tullamore, the first horse to represent the Czech Republic at the Arc last year, pulled out.

Workforce didn't have good position until the last turn and produced an impressive finish on the soft Longchamp ground to avoid some traffic in the final stretch.

``I was always very confident throughout the race, he was always traveling nicely and he had a very good rhythm,'' Moore said. ``There was a bit of scrimmaging, but fortunately he got a nice clean run. He got a tight gap but enough room and he really wanted to do it. He put his head down and stuck his neck out at the end.''

A stewards' inquiry was opened because of the jostling and bumping in the closing stages but Workforce quickly was confirmed as the winner.

``The Derby and the Arc were probably my biggest two ambitions and this horse has supplied them both now,'' Moore said. ``He's a very good horse. Things weren't right at Ascot but the boss put him back in great shape and I was fairly confident today. Just needed a bit of luck and we had that.''

Workforce owner Khalid Abdullah claimed his fourth Arc win, following previous victories with Rainbow Quest (1985), Dancing Brave (1986) and Rail Link (2007).

Teddy Grimthorpe, the racing manager for Juddmonte Farms breeding farm owned by the Saudi prince, said there are no definite plans for next year but he is confident Workforce will continue racing as a 4-year-old.

``I would hope there would be a good chance of staying in training,'' Grimthorpe said.

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AP Sports Writer Jerome Pugmire contributed to this report.