Aidan O'Brien admits George Washington's attempt to conquer America in the 5million Breeders' Cup Classic is a gamble - but one well worth taking.

The Ballydoyle trainer has doubts the four-time Group One-winning son of Danehill will act on the dirt surface.

Going beyond a mile for the first time in his nine-race career is also stepping into unknown territory.

But speaking via a phone-link at an Epsom press conference, O'Brien said: "Obviously, like everybody knows, we've never had a horse with the pace of this horse.

"All the good horses we've had none of them have been able to match the natural pace, and to cruise and quicken like this horse can.

"Everyone says Danehill won't go on the dirt and obviously that's very possible and we won't know that until he runs.

"All we do know is we've never had a horse with this type of class.

"Obviously it's a gamble, but we are hoping maybe he will be able to overcome all of this.

"But he's so quick naturally early and he cruises, so we always thought he'd have a chance of getting a mile and a quarter.

"He's a very rare horse this fellow. Obviously, it is exciting and we don't know what is going to happen.

"He's never been stopping at the end of his races, even though he's never travelled further than a mile.

"We won't know that until he turns into the straight. We just have to hope he jumps and travels and whatever happens after that happens.

"Obviously it is a big disadvantage going out there not having run on the dirt.

"But as we've seen with many of the horses we've ever had, if it is possible to overcome these things, this horse could do it."

BetterBet.com have reacted by making Geroge Washington an 8-1 chance to win the race a week on Saturday.