Race organisers have sounded a warning on the eve of the 33rd America's Cup, saying the size and potential speeds of the two boats poses problems never encountered in the event.
The massive multi-hull yachts of the Swiss holders Alinghi and the U.S. challengers Oracle are capable of speeds of more than 30 knots but neither has ever raced before.
They square off for the first time in tonight's opening race of the best-of-three series off the Spanish port of Valencia.
The huge course totalling 40 miles means the start line could be set anywhere between 25 and 40 miles off the Valencia waterfront.
