The Breeders' Cup Mile is likely to be the next mission for Excelebration as Aidan O'Brien believes the horse is still "on the upgrade" after the four-year-old ran out an impressive winner of the Queen Elizabeth II Stakes at Ascot.

Trainer Aidan O'Brien said there was still improvement in the four-year-old who has raced in the shadow of Frankel until his Ascot win.

"The boys (Coolmore) had it in their head they would go to the Breeders' Cup after Ascot. I think if everything is well, that is the way it is looking," O'Brien told At The Races.

"He has progressed with every run and we have only had him this year so we were experimenting with him a little bit.

"The beauty is this horse is on the upgrade.

"We have learnt a lot about him. He is a very fast horse right up to a mile which he gets well.

"He shows an awful lot of speed and is a very classy horse."

O'Brien would love Excelebration to stay in training as a five-year-old, but accepts the horse is now such an attractive proposition as a stallion.

"It would be a dream for us (to keep him in training) but obviously we have to be realistic," he said.

"He would be very sought after now for breeding.

"He has shown form at two, three and now at four and has shown he is very high class at a mile now."