Rome (AFP) - Organisers of Italy's Palio, the celebrated and historic horse race in Siena, have turned down an offer to take part in Queen Elizabeth II's 90th birthday celebrations, officials said Thursday.

The horse-loving British monarch turns 90 on April 21 and organisers of her equestrian-themed birthday celebrations, to be staged over three days at Windsor Castle in May, approached Palio chiefs in November about the possibility of involving some of the jockeys and horses who race round Siena's Piazza del Campo twice each summer.

But after two months of discussions, the Palio's governing body, the Magistrato delle Contrade issued a statement saying the idea had been shelved for "organisational but also ethical" reasons.

The statement said the proposal had not been put to representatives of the Contrade, the wards of the city which compete against each other in the race.

With the royal organisers unable to provide facilities for a full-scale re-enactment of the centuries-old race, the guardians of the Palio's living traditions were reluctant to countenance a more limited role in the festivities.

"The Contrade would never accept to be puppets in an artificial, choreographed show," former Siena mayor Roberto Barzanti told daily La Stampa.

Current mayor Bruno Valentini was anxious to stress that the city had been flattered by the invitation and that there was no desire to snub the royal household.

"We invite Queen Elizabeth to come to Siena as our guest and to watch the Palio from the balcony of our city hall," he said.