Aidan O’Brien believes Declaration Of War represents possibly his best ever chance of finally claiming victory in the Breeders’ Cup Classic at Santa Anita on Saturday.

Given the prestigious 10-furlong Group One affair is generally run on dirt, it is no surprise European challengers have struggled to make a significant impact as they are neither bred for or have experience of tackling such underfoot conditions.

John Gosden’s Raven’s Pass gave the Europeans a one-two in beating O’Brien’s Henrythenavigator in the 2008 renewal, although that was the year the race was run on a synthetic surface rather than dirt. Andre Fabre’s Arcangues in 1993 remains the only other European-trained winner.

O’Brien’s much-loved ‘Iron horse’ Giant’s Causeway came closer than most have managed to clinching the race on dirt in 2000, going down by a neck to Tiznow, and the master of Ballydoyle believes his latest challenger has even better credentials.

An American-bred four-year-old and briefly trained in the States by Todd Pletcher last year, Declaration Of War has shown his class by claiming the Queen Anne at Royal Ascot and the Juddmonte International at York in Europe this year.

He gave O'Brien further confidence when working on the Fibresand at Southwell recently, and pleased in a spin under former jump jockey Dean Gallagher on the Santa Anita track this morning. Joseph O'Brien watched on from aboard a pony.

The trainer said: “I was happy with everything this morning, the horses went round just to stretch their legs.

“I think Declaration Of War is different to any of the horses I’ve run in the Classic, as he has a different profile. We took him to Southwell two weeks ago because that surface is as close to American dirt in terms of the kickback.

“In that work he followed two Group One winners over a mile, sat in behind them and then quickened up to go clear and he was visually very impressive. We did the same before Giant’s Causeway went for the Classic but he didn’t pull away like this one did.

“Declaration Of War likes to get up there in behind horses and was on the heels of the two in front of him. This horse is by War Front and has Dynaformer in his pedigree and we felt he would have no problem in going back to six furlongs after he won the Queen Anne, but to show how versatile he is he ran over an open mile and a quarter and a half at York and got the trip well.

“The question on Saturday will be how he handles the kickback.

“He had a setback when he was trained in America and we did think about bringing him out for the Classic last year but decided it wouldn’t have been fair on him mentally. But now he is more mentally and physically ready than before, he’s got a fantastic constitution and I think he has got more speed than Giant’s Causeway, who was a horse that could get lazy in his races. This horse is not (lazy).

“It will be Joseph’s first ride on dirt at the Breeders’ Cup and another first for him, but no one knows the horse better. He’s a big powerful horse, and he has been in full work all the time this year. We’ve kept him busy and we are very pleased with him.”

O’Brien was also positive about the chances of Magician, who steps up to a mile and a half for the first time in the Breeders’ Cup Turf.

Winner of the Dee Stakes at Chester before running away with the Irish 2,000 Guineas, the three-year-old has not been seen since finishing last of nine in the St James’s Palace Stakes at Royal Ascot in June.

O’Brien said: “He got a knock before Ascot when he jumped out of the spa and bruised his front legs, and on reflection Ascot was a little bit too quick after what happened.

“He’s been ready to run again for a good while and when we couldn’t bring Camelot (now retired) we decided that we would try Magician.

“Ryan (Moore) thought he was a Derby horse when he won on him at Chester and for the mile and a half race you want a horse that has stayed a mile and a quarter well, although it is a little bit of a concern that he is drawn wide.”