Aidan O'Brien yesterday advised caution about backing the unbeaten double-Derby winner Galileo for the King George & Queen Elizabeth Diamond Stakes at Ascot on Saturday week.

The colt is generally quoted at 4 to 7 favourite for the all-aged championship but while conceding that Galileo is "a strong possible" for the King George, O'Brien stressed that no final decision about his participation had been taken.

"It is not vital that Galileo runs in the King George," said O'Brien. "We would like to give him a run before the Irish Champion Stakes but he could just as easily have a day away from home.

"He has not really done anything since the Derby and he will have to have a piece of work or two before a decision is made. We will see about the King George closer to the time." O'Brien also nominated the Group One Prix Vermeille at Longchamp in September as a possible target if his Epsom Oaks and Irish 1,000 Guineas winner Imagine is to have a warm-up race for the Prix de l'Arc de Triomphe.

"Imagine is fine again after the problem that kept her out of the Irish Oaks and she might have a `prep' before the Arc," he said. O'Brien has an unlikely runner at Killarney this evening as the veteran Kaldan Khan takes his chance in the concluding apprentice claimer. Kaldan Khan is clearly no star but he did okay behind Baku at the Curragh last month and might just be able to cope with the Dundalk sixth Sweet Surrender.

The feature on the second day of the festival is the Heineken Handicap Hurdle, which is worth £19,500 to the winner, and that winner might just be Gift Token. A comparatively light weight could be the key to the Pat Hughes-trained runner who has a further valuable 3lb taken off by Josh Byrne against a strong field headed by Experimental and Best Grey.

Tommy Stack's Serov is upped from sprint distances for the mile maiden and in a bad race could be up to winning.

Arthur Moore can make a quick impression on proceedings with a double in the first two races. Danny Howard's 7lb claim can only be to Tacolino's advantage in the handicap chase while Hot Shots has the experience to cope with Tisrabraq in the novice chase.

A noticeable runner in the conditions race is the John Magnier-owned Independence Hall who hasn't run since appearing at Chantilly last July. However, a safer bet could be the other Sadler's Wells colt, Street Player, who should appreciate the hike in trip from his Cork debut.