ASCOT, ENGLAND (REUTERS) - American raider Animal Kingdom's bid to add a Royal Ascot victory to his Kentucky Derby and Dubai World Cup successes ended in huge disappointment when he finished unplaced in the Queen Anne Stakes on Tuesday.

Animal Kingdom, the 2011 Kentucky Derby winner and the first Run for the Roses champion to run at the Royal meeting since 1936, had been acclimatising in Britain since winning the world's richest horse race, the Dubai World Cup, in March.

But the five-year-old was struggling from halfway as jockey Joseph O'Brien, son of the Irish trainer Aidan O'Brien, came with a powerful late run on Declaration of War to take the opening contest of the prestigious five-day meeting.

"It was an awkward post and (jockey) Johnny (Velazquez) had trouble getting him to settle," Animal Kingdom's trainer Graham Motion told the BBC after the horse trailed in 11th of the 13 runners.

"I don't want to offer to many excuses because he has trained perfectly for the race." Velazquez added: "He didn't put the effort in. It was just not him at all."